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juj.n uii\ u u^, otr l 1923 

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in 2011 with funding from 

University of Toronto 

-9 ^ 

to DEC, 

Illuminating 8 



18 - Yearly. 




16a Copy. 


illuminating Engineering Societp. 

(Founded in London 1909.) 


JAN. 1922 to DEC. 1922 


32, Victoria Street, London, S.W. t 

(Tel. No. Victoria 5215). 


Atherton, ('. A., on Factors determining 
the Legibility of Illuminated Signs .. 230 


Baker. C. A., on Lighting of Public 

Buildings 140 

Beck, C, on Illumination of Miero- 

pes . . • . • • • • • • 173 

Bishop. W. A., on Industrial Lighting . . s7 

Blain. H. E.. at Annual Dinner . . . . 94 

Blandy. Lt.-Col., J.. F., on The Use of 

Light in Aerial Navigation .. ..43,88 

Blok. A., on Recent Developments in 

Lighting . . . . . . . . . . 26 

Bognor. H. W., on The Lighting of tin- 
Milwaukee Art Institute . . . . 260 

Brace, Rt. Hon. Wm„ at Annual Dinner 93 

Brancker, Major-Genera] Sir Sefton, on 

The Use of Light in Aerial Navigation . . 59 

Broadberry. A. K.. on Recent Develop- 
ments in Gas Lighting . . . . . . 22 

Buckley. H.. on Lighting of Public 
Buildings . . . . . . • • 107 

Bullock. A. E., on Lighting of Public 
Buildings 149 

Burt. C. H.. <ni Lighting of Public 

Buildings . . . . . . . . 14<> 

Campbell, ('•.. on Lighting of Public 

Buildings . . . . . . - 1 42 

Campbell. X.. on The Measurement of 

Light . . . . . . . . 2~>."i 

Campbell Swinton, A. A., on Kindred 

Societies (Annual Dinner) . . . . 92 

Chandler. S. B.. on — 

Recent Developments in Gas Lighting 25 
Industrial Lighting . . . . . . 85 

Choyce, C. C, on The Cse of Light in 

Hospitals . . . . . . 1 7."> 

Clark. J. G., on — 

Recent Developments in Gas Lighting 25 
Industrial Lighting . . . . . . *4 

Et. Langton, on Lighting of Public 

Buildings .. ..148 

Colville, J. R., on- 
Fundamental Principles in Industrial 
Lighting . . . . . . 258 

The Cost of. Light 284 

Cunnington. A., on — 

Recent Developments in Gas Lighting 22 
Industrial Lighting . . . . . . 86 

Lighting of Public Buddie .. 144 

Darch. J., on The Use of Light in Hospitals 

L65, L80 

Dates. H.. on School Lighting .. 280 

Davison. I!., on Street Lighting with Gas 229 

Dudding, B. P.. on The Measurement of 

Light . . . . . . . . . . 255 

Elliott. J. YV.. on Lighting of Hospitals . . 177 
Evans, Lt.-Col. Silvester, on The Use of 
Light' in Aerial Navigation . . . . 62 

Fisher. .1. Herbert, on Industrial Lighting 83 
Fry. A. I-]., on Recent Developments in 

Gas Lighting . . . . . . . . 29 

Caster. L. 

Editobials 1. 37, 69, 104, 131, 

159. is:;. 219. 24:;. 267, 291 

Recent Developments in Gas Lighting 28 
Industrial Lighting : [deal Require- 
ments and Practical Solutions ..74,87 

Guests (Annual Dinner) .. .. 92 

Lighting of Hospitals .. ■• 170 

Notes oil Events during the Vacation 297 

Gauvain, Sir Henry, on Light and Life . . 276 
Goodenough, F. YV.. on — 

Recent Developments in Gas Lighting 

Kindred Societies (Annual Dinner) . . 91 

Service to the Consumer . . . . 313 
Cunton. Major H. C. on Lighting of Public 

Buildings 140 

Graves, B. E.,at Annual Dinner .. .. 94 


Bardie. Thus., on Kindred Societies 

(Annual Dinner) . . • ■ ■ • 92 

Harmer. Sir Sydney P.. on The Loss 

Colour of Objects exposed to Light .- 
Harrison. Haydn T., on — 

The Use of Light in Aerial Navigation 60 
i ing of Public Building.- . . . . 142 

Herbert, G., on Industrial Lighting 12s. 310 
Hess, A. P.. on Exposure to Light and 
Condition of the Blood .. .. .. 311 

Hunt, ''.. on Reminiscences of l 

lit ing . . . . . . • ■ ,.313 


I and J 


res. H. E., on The Firefly as an Uluminant 285 

ickson. Sir Herbert, on The Illuminating 
Engineering Society (Annual Dinner) . . 89 
>hnston, E. W.. on Lighting of Hospitals 17'.) 
>nes, L. A., on The Use of Artificial 

Illuminants in Kinema Studios . . 247, 271 
mes, W. J., on — 

Recent Developments in Gas Lighting 29 



.. 306 


Lighting oi Public Buildings 
Ligrrl ing of Hospl 
Dust proof Bow] Fittings 
Project i ir Lamps 

etch, J. .M.. on Cotton Mill Lighting 


unplough, F. E., on The Light-Valve .. 63 

iwford, J. B., on The Illuminating I 

Society (Annual I )inner) . . 89 

berty, W. •!.. on — 

Recent Developments in Gas Lighting 26 
Lighting of Public Buildings. . 135, 305 

ewellyn, F. A., on Lighting ol Public 

Buildings 138 

ickiesh, M.. on A Survej ol Residence 

Lighting .. .. .' 279 

indagen, M. A., on Exposure to Light 
and the Condition of the Blood . . 31 I 


acdonald, W. I)., on A Survey of 
Residence Lighting .. .. .. 279 

iirray, E. T. I!., on Illuminated Signs . . 307 

Gorman, Col. Mervyn, on The Use ol 
Light in Aenal Navigation 

illot. A. C. on Lighting of Public 
Buildings . . . . . . . . 146 

irsons. Sir John Herbert, on The 
Illuminating Engineering Society 
(Annual Dinner) . . . . . . 91 

•arson. S. ().. on The Blinking Effect of 
Neon Lamps . . . . . . . . 304 

ummei. W. on Miner's Lamps . . 302 


Rademacher. W. H.. on Lighting in the 

Food Industries . . . . . . . . 270 

Ramsey. A. <L. on Lighting of Ministry 

of Pensions Building . . . . . . 14") 

Raphael. F, ('.. on Lighting of Hospitals 17fi 
Rayner. E. H.. on Lighting of Public 

Buildings . . . . . . . . 107 

Reiner, J, B., on Portable Inspection 

Lamps for Hospitals .. .. 17."> 

Ryde, J. \\\. on Neon Discharge Lamps 256 


Sandeman, W. ■!.. on Progr< - 

Lighting in relation to Illuminating 
. . 
Selz, C, "u Impregnated Silk Shades 
Shut c. .1. M.. on The Drawing Lower of 
Shop Window 

T. II.. on Lighting of Operating 
Tables in Hospitals 
I, I''., on 
Lighl uiL r of Public Buildings 
The Tuck Photometer 
Sturrock, W.. on The Drawing Lower of 
Shop Window g . . 

i. II.. "ii Recent Developments 
in Gas Lighting 

. A. .I., on The Lighting of the 
Milwaukee Art Institute 
Sykes, Major-General Sir Frederick, on 
The !>,• of Lighl in connection with 
i ion 








Taylor, \. EL, on Developments in Appar- 
atus for Use with the Integrating Sphere 
Tye, L. M.. on Recent Developments in 
i lighting 


Waldram, L. •!.. 

;it Developments in I las Lighting 
The I jdt iu Aerial Navigation 

Industrial Lighting 
Lighting of Public Buildings 
Waller. Major J. P. Ashley, on — 

The Use of Light in Aerial Navigation 
The Lighting of Operating Tables in 
Watson. A. <:.. on The I'se of Light in 

Aenal Navigation 
Watson. I;., "ii Industrial Lighting 
Whyte. A. J., on Recent Developments in 

< las Lighting 
Wilson. A., on Lighting of Operating 

Ta hies m Hospitals 
Wilson, I). R., on Industrial Lighting 
Walsh. .1. W. T.. on- 
Industrial Lighting 
Lighting of Public Building 
Motor-car Headlight s. . 















Access of Daylight, An Important Judg- 
ment on . . . . . . . . . . 152 

Acetylene Candle Fittings . . . . 240 

Acetylene Flares. Use of, for Exterior 

Lighting . . 318 

Acetylene, Dissolved, Applications of . . 182 
Aerial Navigation, Use of Light as an 

Aid to, by Lieut. -Col. L. F. Blandy . . 38, 88 
Aerial Navigation, Use of Light as an Aid 

to (Editorial) 37 

Aerodromes. Night Lighting of .. 231,283 
Ancient Light Cases and Photometric 

Measurements (Editorial) . . . . 133 

Architecture and Illuminating Engineer- 
ing (Editorial) .. . . .. .. 37 

Artificial Daylight 96, 130, 238 

Artificial Daylight, A Proposed Standard 
for . . ' 282 


British Commercial Gas Association, 

Annual Meeting 269, 276 

British Empire Exhibition. The (Editorial) 270 
British Empire Exhibition, The .. ..281 

Church Lighting .. .. .. .. 31 

Circle of Scientific, Technical and 
Trade Journalists : — 

Progress of the CircleJ( Editorial) .. 134 
Visit to New Holophane Showrooms 239 
Visit to L.O.O. Repair Works at 

Chiswick 294 

Colour of Objects in Museums, Effect of 

Light on . . 293, 308 

Cotton Mill Lighting .. .. .. 280 

Croydon Aerodrome. Experiments on 
Night Lighting 231 

Daylight, An Experimental Building for 

the Study of ..126 

Daylight, Access of. An Important. 

Judgmenl . . . . . . 153 

Decorative Interiors. Lighting of ( Editorial) 1 32 

Dispensaries. Lighting of . . . . . . 172 

Distance Control for Gas .. .. .. 9 

Dustproof Lighting Fittings . . . . 306 

Editorials, by L. Gaster 1, 37, 70, KM. 131, 

L59, L83, 219, 245, 267 

Electrical Service . . . . . . . . 266 


Firefly as an Illuminant, The . . . . 285 

Flood* Lighting 65, 242. 282 

Flood Lighting, Development of (Editorial) 4<> 
Fog Signals on Railways, Electric Lamps 

for 128 

Food Industries, Lighting in the . . . . 279 

Gas, Carbon Monoxide in . . . . . . 316 

Gas, Forthcoming International Exhibi- 
tion in Amsterdam . . . . . . 281 

Gas, Industrial Lighting with . . . . 277 

Gas Industry, The. A National Asset . . 316 
Gas Lighting, An Effective Demonstration 

at Croydon . . . . . . 245, 261 

Gas Lighting in Relation to Illumina- 
ting Engineering, by W. J. Sandeman 7 
Gas Lighting in Relation to Illuminating 
Engineering (Editorial) . . . . . . 1 

Gas Lighting in the New Road, St. James's 

Park .. ..257 

Gas Lighting in L.C.C. Schools . . . . 311 

Gas Lighting, Lectures on . . . . . . 313 

Gas Lighting on Railways . . . . 22 

Gas, Shop Lighting with . . . . . . 233 

Gas, Street Lighting by, in Newcastle-on- 

Tyne .. . . 229 

Glare, Avoidance of, 19, 20, 78, 165, 198, 274, 286, 
Glasgow Lighting Association, The . . 314 
Glassware, Terminology and Standardisa- 
tion of (Editorial) . . . . . . 4 


High Pressure Gas Lighting, Developments 

in 29 

Holland, A Visit to (Editorial) .. ..186 

Holophane, Ltd., A Visit to the New 
Showrooms of . . . . . . . . 239 

Home Office Departmental Committee on 
Lighting in Factories and Workshops, 

Third Report of 185 

Home Office Departmental Committee on 
Lighting in Factories and Workshops, 
Third Report of (Editorial) .. .. L85 

Hospital Inspection Lamps. New Types of 302 
Hospitals, Use of Light in (Editorial) . . 159 
Hospitals. The Use of Light in. by .1. 

Darch .. If..". 


Illuminated Signs, New Types of 242. 307 

Illuminating Engineering and Industrial 

Safety (Editorial) 103 

Illuminating Engineering, Progress in 243. 291 



Illuminating Engineering Society (U.S.A.). 

.Sixteenth Annual Convention . . 228, 279 
Illuminating Engineering Society in 

[■many, Annual Meeting of .. .. 232 

Illuminating lEnginecrina society 

(Founded in London, 1909) 
Accounts of .Mi. i m> 

Announcements of New Members 5, 41. 
73. 105, 163, 18 
Lighting i itos to 

Illuminating by 

W. J. Sandeman . . . . . . 7 

The Use of Light as \\ Am to 
Aerial Navigation, by La 
Col. L. P. Blandy 
Industrial Light] Re- 

quirements (Legislative and 
Otherwise) Pr ictic \i. 

Solutions, by L. Gas 
The Lighting of Pi bli< Bi ilium.-. 
Scientific Methods and Ab< iu- 
tectub \ K. I '. 

Rayner, J. W. T. Walsh and 
H. Buckley 
The Lighting 0] Decorative 

Interiors. byCAPT. W. J. Ln 
The Use of Light in Ho 

J. Dakch 
Annual Dinneb on Febbi ari IOtb 
Annual Meeting on May i!">i ii 
Report of < Iounctl fob i 

(November, 1921 May. 1922) . . 
Presidential Address, by Sib John 

Herbert Pabsi 
Thl Illuminating Engini 
Movement in England . . 
Notes on Events During the 

Vac moN, by L. G lsteb . . 
Repobt of the ( !om Pbo- 

gbess i\ Ej ei i bic Lamps \m> 
Lighting Appli \n< es 
Exhibits Illi stb vting Pbogi 
Illumi sating Engineeb 
The " Tuck " Photometer, by I 

E. Stroud ' 

The Holophane " Filterlite," by 

Capt. E. Stroud . . 
New Types of Hospital Inspection 

Lamps, by J. B. Reiner 
The Ceag Pillarless Miners' Lamp, 

li\- \V. Plummer 
The Blinking Effect of Neon Gas- 
filled Lamps, by S. < '. Pearson . . 
Lighting of the New Port of London 
Building, by Capt. W. J. Liberty 
I >us1 proof Bowl Fittings 
Projector Lamps, by \V. J. Jon 
■' [nternalite " illuminated Signs, 

by E. T. Ruthven Murray 
Impregnated Silk Shades, by ('has. 
Incandescent Mantles; and the Safeguard- 
ing of Industries Act . . .... 

Industrial Lighting, Ideal Require- 
ments (Legislative and Othi 
^nj) Practical Solutions, by L, 

l os 





I Ml 








30 7 

30 7 


Industrial Lighting, Fundamental 

Principles of 
Industrial Lighting 69, 74. 128, 185, 197, 

. 310 

Industrial Safety 93,103,294 

Sphere, Developments in th^ 

. 312 

Kinema Studios, Use of Artificial Hlumin- 
ants in, by L. A. Jones .. 247. 271 

Kinema Sti of Artificial Illumin- 

ants in ( Ed . . . . Inf. 246 

Leipsic Pair. Lighting Appliances at the 232 

and Life . . . . . . . . 277 

- itution of the Blood 311 
Human Body, 

on . . . . 128 

on the Human Body. 

on ( Editorial) . . . . 162 


. The Measurement of . . . . 255 

." 1 

. by F. P. Lamplough . . 63 
rig, Popular I of 

(Edito 3 

' . New Apparatus for 

283, 312 

" Luminaire " or " Fixture" . . . . 232 


Maim Lighting, Benefits of .. 21.77 
n>' and Dentistry, Lighting Re- 
quirements in (Editorial) .. 161 
Miiiv Illumination for 173 
Milv, i j, The Lighting of .. 260 
Miners' Lamps . . . . . . 240, 302 

Miner:-' Nystagmus, Inadequate Lighting 

Editorial) . . . . 71 

Miner.-' Nystagmus, Inadeq kiting 

use of. Report of Committee on !I7 
Mines. Lighting of .. .. .. 71. 93, -*7 

Montefiore Triennial Prize, The .. .. 94 

Motor Headlights, Glare from .. .. 286 

Museums, Effect of Lighl on the Colour of 

Objects id .... 293, 308 


National Illi mtnation Committee of 

\t Britain — 

Report of Chairman for 1921 .. 223 

Photometric Definitions and Units .. 22o 

rial Physical Laboratory,. Work of .. is:', 

Neon Discharge Lamps .. .. .. 256 

Neon Discharge Lamps, Blinking Effect of 304 

Tallies in Hospitals. Lighting of 

1(17. 175 



Photographic Efficiency of [Iluminants, 

The . . . . * 253 

Photometric Definitions and I'niis .. 22. r > 
Photometry, Developments in 280, 283, 301 
Picture Galleries, Illuminatio 121, 260 

Port of London Building, Lighting of 137, 305 
Projector Lamps . . . . 101 

Public Buildings, Lighting of (Editorial) 

137, 305 
i'l i'.i.n Buildings, Lighting of: 
Scientific .Methods and Architec- 
\l Requirements, by E. H. 
Rayner, J. W. T. Walsh and H. Buckley 107 

Railway Lighting with Gas. by A. 

Reflection Factors, Convenient Apparatus 
for Measurement of 

Residence Lighting, A Survey of . . 

Reviews of Books and Publications 
Received 36, 68, 129, 181, 241. 265, 289. 

Rou mania, A Visit to (Editorial) 

Royal Society of Arts, Sessional Arrange- 

School Lighting .. .. 31,280,285, 

Scientific and Industrial Research 


Scientific Novelties Exhibition. The 


3 1 7 

2.-. 7 



Scienl ific Progress and Publicity ( Editorial ) 
Searchlights, Use of in Aerial _\a 
Shop Lighting by Gas 
Sho p Light i 

Uing Appa r 

. Factors Effecting Legibility of 
Silk Shades, I mpregnated Fabi ii 
Street Lighting . . 19. 158, 222. 
Street Lighting and Accidents 
Streel Lighting in Newcastle-on-Tyne 
Street Lighting, The Directive S 






. 287 

Thermic Magnetic Flashers .. .. lis 

Topical and Industrial Section :i(i. 65, 95, 

130. 154, 182. 233. 261, 2s7. 315 

Tuck Photometer. The 300 

Tungsten Arc for Projection Work. A New 232 


Ultra-Violet Light, Effects 011 the Eye in 
Kinema Studios . . . . . . . . 273. 

Visibility, Influence of Mist and Fog on 
(Editorial) 39 


Wards in Hospitals, Lighting of 

.. 1(k 


Owing to the great demand for Back Numbers, the cost of Vols. 
I.— XV. will in future, and until further notice, be 25s. UNBOUND, 

ATING ENGINEERING SOCIETY, however, can obtain these 
volumes at a cost of 21s. UNBOUND, and 25s. BOUND. 

Special Cases for Vols. I.— XV. of "THE ILLUMINATING 
ENGINEER" will be supplied at a cost of 4s. each by 


32, Victoria Street, London, S.W.I. 

Some Reasons why you should 

subscribe to . . 

"The Illuminating Engineer." 

Because " The Illuminating Engineer "— 

<J Deals impartially with all illuminants. 

§ Is the official organ of The Illuminating Engineer- 
ing Society (founded in London, 1909) and contains 
full particulars of its proceedings. 

^ Contains up-to-date information on all problems 
connected with natural and artificial lighting, and 
enables you to keep abreast of the times. 

•I Has an extensive international connection, and 
keeps you informed of European and American 

<J Is the pioneer of a movement in Europe from 
which Manufacturers and users of lamps and 
lighting appliances derive great benefit. 

Subscriptions (18/- per annum) and applications for back volumes or single copies 
should be addressed to 



Vacheb & Sons, Ltd., Westminster House, S.W.I.— 4574. 


r 0, 


Sd/fed. ^v^ 





SUuminatino jEnoineering Society. 

(Founded in London, 1909.) 



Tel. No. Victoria 5215. 


Progress in Gaslighting in Relation to Illuminating Engineering. 

A few months ago we drew attention to the value of lighting to the 
gas industry, and urged that this important field should not be overlooked 
owing to the great attention now being devoted to heating and cooking.* 
This view has been strongly endorsed in the comprehensive paper by Mr. 
W. J. Sandeman, of the Croydon Gas Company, read before the Illuminating 
Engineering Society on December 13th, 1921. Mr. Sandeman rightly points 
out that there is ample scope for gas in this field, provided companies are 
keen to keep themselves abreast of progress and to avail themselves of the 
latest developments in illuminating engineering. Success depends largely 
on the recognition that the company not merely sells gas but provides 
good service, showing the consumer how to make the best use of the gas 
supplied and persuading him to discard obsolete fittings and to sanction 
the installation of his lighting on a scientific plan. There is, therefore, 
every inducement to gas companies to co-operate with the Illuminating 
Engineering Society, and encourage members of their staff to become 
familiar with the latest developments in illuminating engineering. 

* Illum. Eng., Oct., 1921, p. 187. 

A 3 


The paper contains ample evidence that this interesting subject is 
being actively studied by the Croydon Gas Company, and includes a most 
comprehensive review of the present position of gas lighting. As Mr. 
Broadberry and Mr. Goodenough remarked it is encyclopaedic in scope, 
and should prove a valuable source of information for future reference. 
The data given illustrating the improvement in efficiency following the 
introduction of superheated cluster fittings are of special interest. It is 
gratifying to observe the emphasis placed on the avoidance of glare. As 
Mr. Sandeman remarks, companies and manufacturers must not be content 
to follow uninstructed public opinion in such matters. They should take 
the lead and gradually educate the consumer, by demonstrations and other 
methods of publicity, to appreciate the benefits of proper shading. We are 
pleased to see that this tendency is well illustrated in many of the latest forms 
of gas fittings, a number of which are illustrated in the paper. Of special 
interest are those of a semi-indirect character, and it is evident that this 
system can be applied to gas lighting as effectively as in the ease of other 
illuminants. The introduction of the vitreosil glassware for low pressure 
as well as high pressure lighting should also prove of great benefit in 
diminishing the ill-effects of glare. 

Amongst the points raised in the discussion may be mentioned the 
question whether data should be presented in terms of " eandlepower 
per cubic foot of gas per hour " or " eandlepower per therm " (or " per 
centi-therm ") ; and whether, similarly, it would not be advantageous to 
express the rules for specific consumption in lumens per centi-therm. This 
is a point on which we shall welcome discussion. Meantime, it i^ agreed 
that when gas consumption is stated, the pressure and calorific value of 
gas used should also be indicated, as is done in the diagrams presented on 
pp. 12 — 13 in Mr. Sandeman's paper. It seems also desirable that some 
shorter phrase should be found than " one cubic foot of gas per hour." 
which occurs so frequently in formulae relating to gas lighting. As has 
recently been suggested the difficulty might perhaps be overcome by agreeing 
to name this unit " one Murdoch." 

Another point that gave rise to discussion was the method of expressing 
the eandlepower of gas lamps. The process of merely taking the mean of 
values in the lower hemisphere may be convenient in practice, but does not 
give us the " mean hemispherical eandlepower " in the accepted sense. 
This is one of those points which will doubtless be settled in due course 
by the work of the International Illumination Commission, and ultimately 
a ruling on the method of rating eandlepower of all illuminants in practice 
should be available. 

Meantime we welcome the evidence in the paper that illuminating 
engineering is being actively studied by the most enterprising gas companies. 
We should like to express our appreciation of the work in this direction of 
Mr. W. A. Bishop, who aided Mr. Sandeman in the preparation of the paper, 
and, in his absence through indisposition, delivered the address before the 
Society. We need not say that it is gratifying to find the younger generation 
taking their share in the application of the principles of illuminating engineer- 
ing to modern gaslighting. We sincerely hope that other gas undertakings 
throughout the country will make arrangements for members of their staff 
to join the Illuminating Engineering Society, in accordance with the practice 
already adopted by a number of leading companies. By this means they 
will ensure their keeping abreast of recent developments in the chief 
illuminants and the principles of correct lighting common to all. 


A Brighter London. 

The campaign being conducted in the Press in favour of a brighter 
London " has assumed various forms, but so far as the literal inteipretation 
of the phrase is concerned it will naturally meet with sympathy on the 
part of illuminating engineers. It is agreed that much might be done by the 
improvement of existing lighting conditions, to make London a more cheerful 
place in the evening. But discrimination in the use of light should be shown. 

Among other measures proposed may be mentioned the display of 
lighted shop- windows after business hours, a practice adopted by various 
stores prior to the war, but which has lately fallen into disuse, chiefly from 
motives of economy. But it may well be urged that a series of well- 
illuminated and tastefully arranged show-windows forms one of the most 
attractive and probably most economical forms of advertisement, and have 
been aptly termed " The Silent Salesman." Apart from their utility to the 
merchant such windows furnish a valuable aid to street-lighting, provided 
the practice is adopted of screening lights and avoiding the exhibition of 
glaring lamps at a low-level. The same remarks apply to illuminated signs. 
The whole question was discussed before the Illuminating Engineering 
Society last year,* and we do hope that those concerned with the movement 
for brightening London will use their influence to avoid glare and excessive 
contrasts in brightness — to prevent light being used in such a way that 
it becomes a nuisance. Let us have not merely a brighter London, but a 
London which leads the world in the skill and discrimination that it 
exercises in the use of light. 

Apart from the display of light in show-windows and the use of 
illuminated signs there are many other opportunities for judicious methods 
of brightening London . Whilst the lighting of its streets doubtless compares 
favourably with that of many Continental cities, there is still much to be 
done in order to place the lighting of London on a more uniform and 
systematic basis, in addition to the possibilities of special decorative lighting 
in important thoroughfares on similar lines to those employed in various 
American cities. Decorative lighting of this description may perhaps be 
difficult to realise at the present moment, but there are opportunities as 
soon as the present economic stringency has become modified. 

A feature that has long been familiar in American cities, the illumination 
of the frontages of important buildings by the aid of flood-lighting, might 
well be adopted with advantage in this city, and we are glad to see that 
several interesting examples of flood-lighting have been initiated by several 
of the leading firms concerned with lamps and lighting appliances. 

Finally it should be remembered that the advantages of improved 
lighting are not confined to its " brightening " and cheering effect. To 
Dr. Chalmers, the celebrated Scottish divine, is attributed the saying that 
" one gas lamp is better than two policemen." Better lighting leads to 
additional safety and security— greater safety of traffic and fuller security 
against crime and disorder. 

* "Light as an Aid to Publicity," Illum. Eng., March, 1921. 


The Terminology and Standardisation of Illuminating Glassware. 

The variety of glassware available for use in modern lighting instal- 
lations is considerable and it is of great importance that the qualities of any 
particular type should be clearly denned. Some interesting comments 
on the subject are to be found in a recent contribution by Mr. S. G. Hibben,* 
who proposes a useful basis of comparison. In the past it has been cus- 
tomary to speak of glassware by certain trade names which, in themselves, 
convey little to the uninitiated as to its properties from the illuminating 
engineering standpoint. Mr. Hibben accordingly suggests that six main 
groups should be adopted namely, (a) crystal, (b) opalescent, (c) homogene- 
ous diffusing, (d) flocculent or foam, (e) cased or coated and (f) opaque or 
silvered. Examples of each variety are specified. Group (c) might also be 
termed " uni-layer diffusing " and group (e) " multi-layer diffusing." Group 
(d) is often described as " milk glass," but this loose term also may include 
(c) and (e). 

The next point to be determined i> the absorption of a globe of the 
variety of glass considered. It is suggested that a division in this respect 
might be made into (i) light density glass, transmitting 87 — 100 per cent., 
(2) medium density glass, transmitting 75 — 87 per cent., and (3) heavy 
density glass, transmitting less than 75 per cent. The limits of this classifi- 
cation might be open to criticism — for instance, that the variety of glassware 
included in the densest group is too large — but the idea involved is to be 

A third characteristic that also requires definition is the character 
of the diffusion of light . Some forms of globes appear evenly lighted all over, 
others show a bright patch in the centre and a less bright periphery. It is 
proposed that the degree of diffusion should be defined in terms of the 
ratio of the brightest area (usually central) to the least bright area (usually 
near the periphery). In making the comparison globes of identical size, 
but composed of the varieties of glassware studied, should be adopted and 
rotated during measurements. A globe which appeared exactly uniformly 
bright all over would have 100 per cent, diffusion. 

Classification on the above lines would at least give us an idea of the 
fundamental properties of the glass for purposes of illumination, though 
there are other qualities to be considered, such as colouration and heat- 
resisting power. One would also welcome polar curves showing the effect 
of the globe on distribution of light, and it is interesting to observe that 
shape of globe has often an important influence in this respect In his 
paper Mr. Hibben also makes some recommendations on the size of globe 
to be used with sources of various candlepower, with a view to keeping 
brightness within suitable limits. Thus a 10 in. globe is recommended 
for a source of 100 candlepower, a 2c in. globe for lamps of 1000 candle- 

There is also much to be done in the study of the effect of superficial 
coatings, glazes and colourings applied to crystal etched and diffusing 
glassware, ventilation problems, and permanency of original qualities as 
regards colour and transmission of light, and we think that the whole 
question might well form the subject of a discussion before the Illuminating 
Engineering Society next session. 

L. Gaster. 

* Elec. Review, Chicago, Nov. 12, 1921. 




Gbe 3Huminating lEngtneerino Society 

(Pounded in London, 1909.) 

The Illuminating Engineering Society is not, as a body, responsible 
for the opinions expressed by individual authors or speakers. 


(Proceedings at the meeting of the Society held at the House of the Royal Society of Arts, 
18, John Street, Adelphi, London, W.C., at 8 p.m., on December 13th, 1921.) 

A meeting of the Society took place as 
stated above. The Chair was initially 
occupied by Mis.Cloudesley Brereton, 
in the unavoidable absence of Mr. F. W. 
Goodenough, who presided during the 
later part of the proceedings. 

The Minutes of the last meeting 
having been taken as read the Hon. 
Secretary read out the names of new 
applicants for membership as follows : — 

Mr. W. A. Bishop then read the paper 
opening the discussion on "Progress 
in Gas Lighting in relation to Illuminating 
Engineering." The paper was illus- 
trated by a variety of lantern slides, and 
an interesting discussion ensued in which 
Mr. F. W. Goodenough (Chairman), 
Mr. A. E. Broadberry, Mr. A. Cunning- 
ton, Mr. A. H. Stevens, Mr. J. G. 

J. R. Milnes 

E. E. Stockwell 

Electrical Engineer, P.O. Engineering Dept., 

Carrington Road, Nottingham. 
Managing Director Messrs. Stoekwell & Ohms. 

Ltd., 164a, Pentonville Road, London, X.l. 

The names of applicants announced 
at the previous meeting on November 
15th* were read out again, and these 
gentlemen were formally declared 
members of the Society. 

The Chairman referred to the indis- 
position of Mr. Sandeman, to whom 
they all wished a speedy recovery. In 
his absence the paper would be pre- 
sented by Mr. W. A. Bishop, who was 
associated with the Croydon Gas Com- 
pany, and had assisted Mr. Sandeman 
in its preparation. 

* Illttm. Eng., Dec. 1921. p. 23L 

Clark, Mr. S. B. Chandler, Mr. W. J. 
Liberty, Mr. A. Blok, Captain E. 
Stroud, and Mr. L. Gaster took part. 

A cordial vote of thanks to Mr. Sande- 
man and Mr. Bishop was passed unani- 
mously. The Chairman announced that 
the next meeting would take place 
towards the end of January, 1922, when 
a discussion on the Use of Light as an 
Aid to Aerial Navigation would be 
opened by Lieut.-Col. Blandy, D.S.O., 
R.E., Major-General Sir Frederick 
Sykes, Controller-General of Civil Avia- 
tion, had kindly consented to preside 


[a) Pear-shaped Globe (clear 
or frosted glass). 

(«/) Typical Semi-indirect Fitting. 

(b) Pear-shaped Globe with 

etched band to diminish 
glare within range of eye. 

(e) Single inverted Burner with 
Vitreusil Chimney. 


(r) Aluminium Case and 
vitreosil cylindrical 

(/) Bowl fitting for use near ceiling. 




By W. J. Sandeman (Croydon Gas Company). 

(Presented at the meeting of the Illuminating Engineering Society held at the House of the 
Royal Society of Arts, 18, John Street, Adelphi, London, W.C., at 8 p.m., on Tuesday, 
December 13th, 1921.) 

It has been suggested to me that, so 
many interesting developments in gas 
lighting having taken place during the 
past few years, the time is ripe for a 
survey of the progress that has been 

Before, however, proceeding to recent 
progress it may be well to give a brief 
review of the general development of gas 
lighting. Progress in respect of efficiency 
is conveniently illustrated by the 
transition from (a) flat flame burners to 
(b) upright incandescent burners, (c) in- 
verted incandescent burners, (d) super- 
heated (small mantle) multiple-burner 
lamps, and (e) high-pressure lamps. The 
primary object, in these successive 
changes, has been the attaining of a 
higher candlepower for a given con- 
sumption of gas. To-day, as is well 
known, the illuminating power standard 
(under which gas was sold) has been 
superseded by the calorific power standard 
— the aim now being to obtain a suitable 
heating value from the gas. 

Whereas the old flat flame burner 
depended almost wholly upon the illu- 
minating power of the gas, the incan- 
descent mantle depends mainly on flame- 
temperature. Although in incandescent 
lighting the candlepower depends to some 
extent upon the calorific value of the gas, 
it is primarily affected by the pressure 
at which the gas is supplied. In the 
days of flat-flame burners 5/lOths inch 
pressure (water column) was considered 
adequate ; for incandescent burners 
pressures of 25 — 30 tenths are needed if 
a really " full " mantle is to be secured. 

It is safe to -say that with a 16 candle- 
power gas — under the old illuminating 
power standard — the efficiency of an open 
flame burner was of the order of 2 — 25 
candles per cubic foot. Specially pro- 
portioned Argand burners gave a some- 
what higher duty, 3 — 35 candles per 

cubic foot. In spite of its still lower 
efficiency to-day, open flame burners still 
prove useful in certain cases, i.e., as a 
" safety " light in places where only an 
emergency glimmer is required. Various 
cumbersome devices for increasing the 
efficiency of open flame lighting by super- 
heating the gas with its own products of 
combustion led to an improvement to 
about 8 candles per cubic foot. These 
devices are now chiefly of historic 
interest as indicating methods which have 
since proved valuable in connection with 
incandescent gas lighting. 

The first great stride in gas lighting 
was the discovery of the incandescent 
mantle in 1885. As already explained, 
the luminosity of a mantle depends 
mainly on flame-temperature, which may 
attain 1 ,700° Centigrade in the extremities 
of a well-aerated Bunsen flame. It is 
interesting to note in this connection that 
some authorities describe as " bright 
white " or " dazzling white " any surface 
raised to a temperature in the neigh- 
bourhood of 1,400—1,600° Centigrade. 
The Welsbach " C " or standard size 
upright burner gave about 16 candles 
per cubic foot of " 14-candle " gas — a 
notable advance. Subsequent improve- 
ments (whereby a larger proportion of 
air was drawn into the mixing tube) 
were embodied in the " Kern " burner, 
which yielded on a " 14-candle " gas 
about 18 candles per cubic foot. The 
next advance of importance " self- 
intensification " was achieved by pro- 
viding the " Kern " burner with a long 
chimney, the effect of which was to draw 
in an additional supply of primary air, 
enabling a larger amount of gas to be 
consumed by the same mantle, and 
promoting a higher degree of primary 
aeration of the Bunsen flame. The 
resulting increased flame-temperature 
brought the efficiency up to 20 candles 

B 2 


per cubic foot. It also enabled larger 
mantles to be used, and 300 and 600 
candlepower units to be produced. 

(All the efficiencies recorded above 
refer to the mean of a number of equi- 
distant angular readings, taken all round 
the source, as obtained in the past.) 

Inverted Burners. 

Inverted burners made their appear- 
ance about 1900, and are to-day the 
chief source of artificial gas-lighting for 
domestic purposes. For the latter re- 
quirement they are made in three 
standard sizes, viz. — universal, medium 
and bijou. On average present day gas, 
an efficient and well-adjusted inverted 
burner should yield a duty of about 20 
candles per cubic foot. For the three 
sizes mentioned, the consumption and 
candlepower at 30/10ths pressure are 
approximately as follows : — 

„ ( ionsumption in ,, ,. 

Typeof Burner. ,.„,, ft ',„.,. ,„,- Omdlepower. 










Larger, smaller and intermediate 
mantles can be fitted to appropriate 
burners. For passages, staircases, etc. 3 
there is now available a very efficient 
little burner and mantle consuming one 
cubic foot per hour and yielding 20 

The larger (No. 6) mantle, introduced 
in 1912, and used in twos, threes and 
fours, was regarded as the most advanced 
form of low pressure gas lamp (until the 
recent adoption of superheated burners 
carrying small mantles) and attained a 
maximum efficiency of 30 candles per 
cubic foot. Following the single inverted 
burner, multiple-hurneT lamps (2, 3, 4, 5, 
and 6 burners) using either No. 4 or No. 6 
mantles (the number indicating the 
approximate hourly gas consumption in 
cubic feet) were introduced. Each burner 
was equipped with independent air and 
gas regulators. 

(The efficiencies recorded in the above 
section on inverted burners are based on 
present day figures, obtained as the mean 

of a number of equidistant angular read- 
ings taken in the lower hemisphere. The 
value given for " No. 6 " mantle lamps, 
however, only applies under favourable 
circumstances and on pre-war gas of, say, 
530—550 B.Th.U.s (gross) per cubic foot). 

Inverted " Cluster " Lights. 

This leads us to the most recent 
development in low pressure gas lamp 
construction, namely : — 

(a) The provision of a " Superheater " 
through which the gas and air mixture 
passes to the burners in a pre-heated 

(6) The employment of small mantles 
in '" cluster " form. 

(c) The use of a single gas and air- 
n'L'ulator for the whole of the burners. 

It is now an accepted fact that such 
pie-heating leads to higher flame tem- 
perature and hence increased mantle 

The use of a series of small mantles, 
in a cluster, in preference to a single big 
mantle, has also advantages. Small 
mantles have proved superior to big ones, 
chiefly for the following reasons :— 

(a) The strength, and hence the life, 
of a mantle is in inverse ratio to its size. 
Maintenance records prove that the 
average life of a No. 2 mantle is appre- 
ciably longer than that of a No. 4 or 
No. 6. 

(b) There is considerable disparity 
between the shape of an inverted bunsen 
flame and the shape of a mantle, and the 
larger the mantle the smaller the propor- 
tion of its area that is brought to full 
incandescence. Recognition of this fact 
has led to the general use of No. 2 
mantles, which are proportioned to 
closely fit the normal flame and deflection 
of an inverted burner. Hence a second 
advantage of the small burner is its 
greater efficiency. Again, the small 
flames are short and stiff (approximating 
to a blow-pipe flame), while the larger 
flames have a distinct tendency to 
oscillate. This fact of increased " steadi- 
ness " is another point in favour of the 
small mantle. 

The advantage of having a single gas 
and air regulator to control a group of 
mantles (instead of one for each) is that a 


slight turn either way suffices to bring the 
whole lamp into its best condition. 
Regulation difficulties are accordingly 
reduced to a minimum, and accurate gas 
and air mixtures readily ensured. 
" Cluster-lights " of this type are now 
widely used for both indoor and outdoor 
lighting. Experience has shown that the 
cost of maintenance of such a light is less 
than would be the case for single large 
burners of similar total candlepower, 
partly on account of the greater strength 
of the small mantles, and partly on 
account of the saving of glass-ware 
maintenance, as a " cluster " can be 
equipped with a single large globe. 

Generally speaking, we have found 
that multiple-burner lamps with small 
superheated mantles are about 40 per 
cent, cheaper in regard to maintenance 
and give the same candlepower on 
50 per cent, less gas than would be used 
by upright burners. 

In the latest forms of low-pressure 
lighting units a duty of 40 candles per 
cubic foot has been attained, through the 
employment of superheated multiple- 
burners carrying small mantles.* An 
alternative method of obtaining increased 
flame-temperature and greater brightness 
of the mantle is by so-called " high- 
pressure " gas lighting. 

Increased efficiency may be obtained 
either by the use of gas under pressure, 
or by applying such a pressure to a 
mixture of air and gas. Of the latter 
method (illustrated in the " Selas " 
system) good results are reported, but 
it has not come within our experience. 
The most general (" Keith ") system is 
based on the use of " high-pressure " gas, 
a positive rotary compressor being 
employed to raise the pressure to 3 lb. 
per square inch. This pressure imparts 
a sufficient a elocity to the explosive air 
and gas mixture to enable it to burn and 
remain " stiff " at the nipple without 
lighting back, and as the degree of 
primary aeration becomes more complete, 
and nears the explosive limit, the flame 
becomes increasingly short and hot. 

* Messrs. Wm. Sugg and Co., Ltd., the 
pioneers of the superheated " cluster," listed 
their efficiencies at " 40 — 45 candles per cubic 
foot " on pre-war gas of, say, 530 — 550 B.Th.U.s 
(gross) per cubic foot, values being based on 
the mean of a number of equidistant angular 
readings taken in the lower hemisphere. 

In addition to its provision of '* extra " 
aeration, the " Keith " lamp is fitted 
with a fixed gas-nipple, specially long 
mantle and an air regulator, and is 
designed to embody all the three methods 
of intensification, viz. : (a) increased gas 
consumption for a given size of mantle, 
(b) more complete primary aeration of the 
Bunsen, and (c) pre-heating of the gas 
and air mixture prior to combustion. 
These features result in the highest 
efficiency yet attained in gas lighting, 
namely 55 — 60 candles per cubic foot.| 
An interesting development in the 
" Keith " system has been evolved for 
use in classes of factories where the air 
is apt to become filled with small solid 
particles in suspension. This " duct " 
system involves the use of tubes of fresh 
air, led in from outside the building, 
the high pressure gas being connected 
at various points. Each connection 
supplies, by means of one injector, a 
number of high pressure burners, and 
this injector, being of large capacity, is 
not likely to get choked. 

Methods of Distance Control. 

Having now dealt with developments 
in connection with lighting efficiencies, 
a few words may be said on the control 
of lighting units — a matter of very great 
consequence to gas undertakings, in view 
of the advantage usually credited to 
their chief competitor, electric lighting, 
in this respect. Numerous devices have 
been introduced in the past to secure 
simultaneous turning on of a gas-supply 
and ignition by some supplementary 
means. Amongst these devices may be 
mentioned the use of platinum sponge 
(sometimes attached to the mantle), 
which becomes hot when exposed to a 
stream of gas, and of an electrically 
heated wire" or a high tension electric 
discharge (" jump-spark "). The elec- 
trical methods are still used to some 
extent, but the other has not survived. 

t Messrs. James Keith and Blackmail Co., 
Ltd., have stated this value, which applied with 
pre-war gas of, say, 530—550 B.Th.U.s (gross) 
per cubic foot, but apparently must be under- 
stood to relate to the maximum photometric 
reading taken horizontally, without reflector. 
Personal present day observations, taking the 
mean of equidistant angular readings in the 
lower hemisphere, reveal an average efficiency 
of a little over 45 candles per cubic foot. 



The chief point to be observed is that 
any such system, in order to obtain 
extensive use, must be absolutely reliable. 
Any method, however ingenious, which 
requires constant attention in order to 
ensure reliability, will not find favour 
with the ordinary consumer. 

In general, therefore, gas-lighting still 

involves the use of a byep;i 

The simplest method (1) is the ordinary 
byepass cock and chains. The pneu- 
matic valve and switch (2) is used a 
good deal in houses, halls, etc., and 
answers well if given occasional attention. 
Method No. (3), Sugg's mercurial seal 
and flash light cup and ball, is much 
used for controlling distant lights in 
large interiors (churches, halls, offices. 
schools, etc.), and has proved quite 
reliable. This device permits of the 
lighting and extinction of any number 
of lights from one control board. Any 
number of units can be operated, but 
where it is desired to " sectionise " the 
control, separate supplies, each with a 
cock, have to be run. Each lamp 
requires a byepass supply from a common 

The latest form of control (4), Sugg's 
automatic diaphragm distance-lighter, 
fulfils the same purpose as the device 
just described, but has the great advant- 
age of eliminating a separate byepass 
supply. It functions by means' of a 
two-holed control cock which allows, 
when in the " off " position, sufficient 
gas to pass (without raising the leather 
diaphragm valve off its seating) to keep 
the byepass going. The length of the 
byepass jet is regulated by a set screw. 
When in the "on" position the full 
bore of the cock permits of an increased 
pressure of gas raising the valve to 
momentarily shoot out the flashlight 
(which reduces at once to a tiny byepass 
jet when the lamp is alight), and pass the 
lull supply of gas to the burners. This 
ingenious device has answered very well 
and has had numerous applications. 
In particular it is a great convenience 
to tradesmen who wish to control their 
outside lamps from the interior of the 

For the control of high-pressure lamps 
(we have just commenced an installation 
of 30 large units, 1,500 and 1,000 candle- 

power * in an ironworks) the lighting and 
extinction can be conveniently effected 
by Keith's special control device. In 
this particular installation the lamps are 
to be operated in " pairs " and " threes " 
in various bays. As is well known, 
various methods of central control by 
pressure waves have been adopted in 
some districts for street-lighting. The 
advantages of such methods naturally 
vary according to the nature of the 
district. In Croydon and district most 
of the street lamps are lighted by hand, 
although clockwork controllers are used 
in outlying districts and on certain " far- 
off " lamps. 

(ihlssiniri <i,i'l Fitlniqs. 

Turning next to fittings and globes, 
I may say that in this direction, also, 
there have been marked advances during 
recent years, and that by proper design 
it is possible to obtain practically all 
the conditions aimed at with electric 
lighting. Semi-indirect lighting, for 
instance, has been widely used during 
recent years, and can be applied with 
particular convenience to the " cluster " 
burners, previously referred to. As all 
illuminating engineers are aware, it is 
not always easy to induce consumers 
to adopt fittings that screen the light 
and distribute it in the approved manner. 
We have, however, made a practice of 
emphasising the great advantages of 
eliminating glare, even though some 
absorption of light may be occasioned. 
The percentage of light transmitted 
through various materials may be 
estimated somewhat as follows : — 

Per cent. 

Clear glass 90-95 

Lightly " frosted " glass . . 80-85f 

" Vitreosil "" (open bottom 

cylinders) 80-85 

Heavily " frosted " glass . . 70-75 

Opal glass 45-60 

Naturally, the light used in the room 
is not necessarily diminished in this 
ratio, as glassware does not, as a rule, 

* " Nominal candlepower." The mean of 
equidistant angular readings in the lower 
hemisphere is about 890 for a " 1000 candle- 
power " lamp, and about 1,290 for a " 1,500 
candlepower " lamp. 

f Note. — May be as high as 90. 



completely enclose the source. In the 
case of " open-mouthed " reflectors, for 
example, the loss of light arising through 
the use of opal or other light-diffusing 
glass is comparatively slight. In low- 
pressure superheated " cluster " lighting 
an average efficiency of 35-37 
candles per cubic foot may be 
expected when clear glass globes and 
enamelled steel reflectors are used. If 
lightly " frosted " globes are substituted 
the efficiency becomes about 31 or 32 
candles per cubic foot. About the same 
duty is derived from lamps equipped 
with circular and octagonal opal reflectors 
and clear glass globes. Slightly less 
duty is obtained by employing partially 
" frosted " globes (usually lower half) 
in conjunction with opal reflectors, and 
as this is the system of lighting most 
generally adopted by us for direct 
illumination, it may be of interest to 
say that we make our calculations 
on the basis of 30 candles per cubic 
foot, which we have found in practice 
to be a fair average efficiency. 

The average efficiency of units with 
pear-shaped " frosted " globes (such as 
we have adopted for church lighting) is 
of the order of 25-28 candles per cubic 
foot. We allow 25 candles per cubic foot 
in our calculations, and from results 
'.btained this figure seems to be fairly 

(All the figures quoted in this section 
represent the mean of a number of equi- 
distant angular readings taken in the lower 

The values given may be of interest, 
as illustrating the effect of using different 
types of glassware, etc. One finds that 
such variations are apt to be overlooked, 
estimates of resultant illumination being 
based on the duty obtainable from un- 
screened mantles. In the case of large 
units used without reflectors we have 
found it convenient to leave a clear upper 
and lower area of the globe and to utilise 
a central " frosted " band which is 
helpful in diminishing glare at the eye- 
level, but allows of a powerful illumination 
vertically and horizontally. At this 
point I should like to emphasise the 
importance of polar curves of light- 
distribution of units being more generally 
furnished by manufacturers. These 
curve; are of great value in tracing the 

illumination resulting from a given 
spacing of lamps, and following the read- 
ing of this paper a few typical diagrams 
will be shown upon the screen. 

Various facts and figures relating to 
these polar curves are given in the 
table on page 14. 

A noteworthy development in con- 
nection with globes and fittings has been 
the introduction of vitreosil heat-resisting 
glassware, which is now widely used. 
This material is similar to the silica cups 
first introduced for use with high-pressure 
lamps, but is now being generally applied 
to low-pressure lighting. The primary 
advantage claimed for chimneys and 
globes of this description is their tough- 
ness and power of resistance to changes 
in temperature, draughts, etc. In spite 
of the relatively high initial cost, their 
use has been amply justified by reduced 
costs of maintenance, as they break but 
rarely. Moreover, the life of mantles is 
prolonged, partly because they are not 
liable to be destroyed through glass- 
breakage, and also because they may 
often be continued in use when partially 
broken, as the impact of the flame on 
the vitreosil glass does not damage it. 
The glassware has a milky appearance, 
but, from the standpoint of avoiding 
glare, this may be considered an actual 
advantage. The fact that the material 
can be brought so close to the mantle 
leads to compact design, and the trans- 
lucent surface, which diffuses the light- 
but conceals the actual shape of the 
mantle, is often of value in enabling an 
inverted burner to be introduced into 
an upright fitting. Thus the advantages 
of the more efficient inverted burner are 
obtained without affecting the desired 
impression of an upright standard. One 
interesting feature of the use of this 
material is that the colour of the emerging 
light is appreciably modified, becoming 
somewhat more golden in tint. As the 
mantle is also completely screened from 
view, it is difficult, at first glance, to tell 
whether many fittings contain a gas 
mantle or an electric filament. In 
passing, one interesting feature of this 
glassware may be mentioned. It is 
possible to place mantles in closed globes, 
having -only narrow slits at the side, 
through which air can penetrate. Globes 
of this description are particularly 



C/KNIh ' CS 

(a) 4-Light Littleton Lamp. 

(ias consumption : 9-8 cu. ft. 

„ press i lie 


25 luths. 
514 B.Th'.U, 


(b) 4-LlGHT Semi-Indirect. 

Gaa consumption : 10 en. ft. 
„ pressure : 25/lOths. 

. value : 481-7 B.Th.U, 

(r) 6-Light Pattern. 

Gas consumption : US cu. ft. 
„ pressure : 25/lOths. 

,, value : 4996 B.Th.l - . 

((/) ti-LiGHT " Margate " Lamp. 

Gas consumption : 15 cu. ft. 
„ pressure : 25/10ths. 


498-3 B.Th.U. 

(e) 6-Light Swanley. 

Gas consumption : 15 cu. ft. 
„ pressure : 25/lOths. 

„ value : 510 B.Th.U 












valuable in cases where it is desired to 
avoid possible dropping of hot parts from 
the mantle. I desire to emphasise the 
importance of constant pressure in con- 
junction with incandescent gas lighting. 
This can be readily attained by the use 

complete primary aeration now obtaining 
in bunsen flames tends, as we have all 
doubtless experienced, to shorten the 
flame ; hence, it is not an easy matter 
to-day to completely and economically 
fill a " C " mantle. Again, where No. 6 

Details of Polar Curves to be shown at the Meeting. 

of No. 2 

Lamp fitted 
with : — 

Total con- A 


1 , • consump- 
m dime . ' 

feet per t,on ln 

hour of ™ b ^et 

"super- P erhour 

heated" . per 

burners. bumer " 

in tenths 
of an inch 


< 'alorific 

value of 

gas in 



per cubic 


power — 

10° to 90° 



per cubic 

foot of 



15° " Extensive " 
enamelled steel 
reflector and 
clear globe. 



25 499-6 




Clear globe 
only ; no 



25 484-8 




35° " Extensive " 
opal reflector 
and clear globe. 








reflector in 
ordinary 16-in. 
street lantern. 








15° " Extensive " 
opal octagonal 
reflector and 
clear globe. 








10° " Extensive," 
enamelled steel 
reflector and 
clear globe 
(outdoor unit). 








35° " Extensive " 
opal reflector 
and clear globe. 








40° " Extensive " 
enamelled steel 
reflector (no 



25 510-0 



of a service governor, which ensures 
constant accuracy of adjustments and 
eliminates wastage through excess of 
pressure reaching the points of consump- 
tion. Further, I would like to add the 
importance of using every endeavour to 
induce consumers to discard upright 
burners in favour of inverted. The more 

mantles are in use, the consumer should 
be approached regarding their conversion 
to either the No. 4 or No. 2 size. In 
Croydon we have converted quite a 
number to take these two sizes of 
mantles — the No. 4 without " super- 
heater," and the No. 2 with " super- 




«</ u^ S» 


Figs. — Typical Polak Curves of Light 

(a) 150 candlepower Lamp, Indoor Pattern 
with Deep Shade. 
This gives a somewhat concentrated light, 
especially suitable for Bench Work, the highest 
candlepower being given immediately under the 

(6) 50 candlepower Lamp, Standard Pattern. 

This shows distribution of light with ordinary 
enamelled reflector. 

(c) 500 candlepower Lamp with Circular Glass 
This shows the special distribution of light 
and diffusion above the horizontal, and forms 
an interesting comparison with (6). 

80- so . SO 




Simple Illuminating Engineering Data. 

Let us turn now to some of the methods 
which we commonly use in making 
calculations of illumination. A great 
deal has been written on this subject and 
it is now generally agreed that illumina- 
tion can be calculated with quite sufficient 
accuracy for practical purposes, provided 
the performance of the lamps is known. 
By the aid of the polar curve one can, of 
course, determine the resulting illumina- 
tion from a given lamp in a certain 
position, and the combined effects of a 
series of lamps can be similarly calculated. 

But in dealing with commercial gas 
lighting it is desirable to have rules of a 
very simple and practical character and 
we have found that the general results 
we have deduced connecting gas con- 
sumption with resultant illumination 
apply quite accurately enough in practice. 
In the lower hemisphere the mantle acta 
like a luminous point and the candle- 
power in different directions does not 
differ very widely. This natural distri- 
bution of light is, of course, altered by 
the effect of reflectors, but here, again, 
the types of units with which most of 
our work is done give the same general 
types of polar curves. In special cases, 
when a focusing effect for local lighting 
is needed, we can obtain a curve with a 
much larger vertical component by 
employing a '* deep " or concentrating 

We have found that the consumptions 

required to produce a given illumination 

over a certain working area with direct, 

semi-indirect and indirect lighting are 

approximately in the ratio of 1, lg, 2. 

This, I believe, is in accordance with 

experience in electric lighting. Assuming 

that modern low pressure multiple small 

mantle lamps with superheated burners 

are used, one finds that the amount of 

gas allotted should be approximately 

as follows : — 

' Consumption in cubic feet 

„ . ,. . .. of gas per hour per foot- 

System of lighting. can % e ^ er squarp 1 f J t of 

surface illuminated. 

Direct lighting . . . . 0*008 

Semi-indirect lighting . . 0*012 

Indirect lighting . . . . 0*016 

The value for " Direct Lighting " refers 
to units of an extensive type. 

The values for all these systems assume 
30 — 40 per cent, diffuse reflection from 
light interior decorations. 

It is interesting to observe that these 
figures are in close accord with some 
furnished, quite independently, by your 
Honorary Secretary in his book on 
Illumination. The consumption is, how- 
ever, estimated to be somewhat smaller, 
by reason of improvements that have 
since taken place. 

Bearing in mind the efficiency attri- 
buted previously to high-pressure gas 
lighting, it would seem that with direct 
lighting of this description 0*0053 cubic 
feet per foot-candle per square foot 
illuminated would be a fair value. This 
is approximately equivalent to a duty 
of 45 candles (mean of equidistant 
angular leadings in lower hemisphere) per 
cubic foot. With semi-indirect and in- 
direct met hods the allowances would be 
Increased in accordance with the propor- 
tions indicated above. 

I am aware that semi-indirect lighting 
has certain advantages not taken into 
account in these calculations, for example, 
the greater freedom from glare and the 
greater proportion of light devoted to 
the illumination of the upper part of 
the room. But, irrespective of these 
points, it seems desirable to work to a 
certain illumination in foot-candles on 
the working plane. 

Methods of Spacing. 

The above method of calculation 
assumes that we are aiming at the pro- 
duction of a uniform illumination over 
the working area, and this in turn 
assumes certain proper methods of spac- 
ing units. Some illustrations will be 
given showing appropriate spacing for 
various types of lamps. Conditions in 
this respect may vary according to the 
type of unit adopted. But generally 
speaking experience shows that it is 
impracticable, with direct lighting, to 
obtain reasonably uniform illumination 
with units spaced at a distance apart 
greater than twice their height from the 
working plane. A very usual height 
of suspension above floor level for direct 
units of medium power is 8| — 10 feet. 

In narrow buildings (up to 30 feet wide) 
units are commonly spaced down the 
centre line, outside lamps (in a row of 



— -$ 


~e e e~-« 





j— * 




Height of 

Working Plane 



Height of 

Working Plane 




tliree or more — according to the length) 
being half the distance from the wall 
that they are from the centre lamp 
(or intermediate lamps). In approxi- 
mately square interiors (30 — 40 feet wide 
and over) we divide the area into squares, 
with lights at their centres in accordance 
with the right spacing ratio. Large 
lofty buildings are commonly lighted 
by lamps spaced at a distance apart 
equal to only half their height from the 

The height in such cases would prob- 
ably be 18—20 feet. The wide dis- 
tribution curve from six and eight 
burner No. 2 mantle lamps with octa- 
gonal reflectors is particularly suitable 
for the lighting of halls. Effective 
illumination over a width of 25 — 30 feet 
is produced from lamps of this type 
when mounted 13 — 15 feet above the 
floor-line. Semi-indirect lights have, in 
comparison, a narrower distribution, 
being effective over a width of about 
15 feet only. In buildings, say, 30 feet 
wide one cannot obtain such efficient 
illumination by placing a single row of 
lights down the centre as is possible 
with lamps equipped with " extensive " 
reflectors. Two rows of semi-indirect 
lamps would here be necessary. For 
each type of lighting unit it seems 
highly desirable to provide appropriate 
spacing rules, and this, I think, is a 
matter to which manufacturers of gas 
lamps should give immediate and earnest 

Values in Foot-candles. 

As regards the order of illumination 
usual in practice, I find that in our 
installations the range of illumination, 
according to the purpose served, is from 
about one to six foot-candles. The upper 
values 4? — 6 foot-candles are considered 
a " super-effect " necessary where work 
of a fine character is done. Even these 
" super" values may be exceeded when 
local lighting for very fine operations 
is adopted. In such cases we aim at 
providing supplementary top-lights (out 
of the normal range of vision) giving 
a general illumination of about 0*5 foot- 
candles, which prevents the contrast 
between the brightly-lighted area under 
local lamps and the general brightness 
of surroundings being too severe. 

Corresponding to this range of illumina- 
tion we have certain convenient allow- 
ances in candlepower per square foot. 
It is quite realised that this method of 
prescribing lighting needs discrimination. 
Naturally, it is assumed that proper 
methods of shading, etc., are adopted : 
mere prescription of candlepower without 
attention to this factor would not ensure 
adequate illumination. Assuming, how- 
ever, due appreciation of this fact, the 
" candlepower per square foot " basis 
proves useful. We commonly allow : — 

per sq. ft. 
For sufficient light for 

simple operations . . 04 — 0"6 
For medium lighting . . 05 — 075 
For bright lighting .. 075— 10 
For very bright lighting TO — L5 

In direct lighting systems these values 
in general correspond with a range of 
illumination of from H to 6 foot-candles. 
It is, perhaps, worth recording that with 
fairly large units hung well up and fitted 
with " extensive " reflectors one may 
assume a resulting illumination on the 
working plane equal to four foot-candles 
per candle per square foot. 

In offices and class-rooms we would 
usually provide standard (2) ; for fine 
work standard (3). 

A sound rule for general purposes is to 
allow one candle per square foot for 
exceptionally bright lighting and one 
candle per two square feet where only a 
moderate effect is required. 

All such rules are naturally affected 
by the heights of interiors and the colour 
of the surroundings. Lofty rooms and 
interiors with specially dark decorations 
are usually found to require the higher 
scale of illumination given in the above 
table. In working back from candle- 
power to the gas consumption required 
one would naturally make the proper 
allowances in view of the installation 
being direct, semi-indirect or indirect. 
Co-efficients of reflection for various 
coloured papers have often been quoted. 
Whereas with white surfaces 70 — 75 
per cent, of light is reflected, with cream 
colour the value is frequently only 
50 — 55 per cent. ; pale green 40—45 per 
cent. ; yellow 35 — 40 per cent. ; stone 
grey 15 — 18 per cent. ; while medium 



browns, reds, greens and blues may only 
reflect 10—12 per cent., and dark 
shades of these colours as little as 5 per 
cent. The effect of such variations on 
resultant illumination is obvious, but it 
is apt to be overlooked and requires to be 

Avoidance of Glare. 

Apart from the provision of sufficient 
illumination, the desirability of avoiding 
glare deserves most careful attention. 
This term includes unduly severe con- 
trasts. It is certainly desirable to avoid 
any completely unscreened mantles 
within the direct range of view, and it is 
also bad practice to leave the upper part 
of a room in complete obscurity, as is apt 
to happen when opaque reflectors are 
used. Certain cases occur where special 
measures to avoid this last effect are 
needed. In schools and other places 
where the use of glass in overhead 
lights is considered undesirable, and 
even forbidden, one can construct metal 
reflectors with a " top-gap " through 
which a certain proportion of the light 
passes to the ceiling. 

Street Lighting. 

This has great possibilities, but can 
only be treated briefly. It has been 
very ably dealt with by Dr. Thomas in 
his recent address to the Public Works, 
Roads and Transport Congress. Stress 
has been laid on the importance of 
uniformity of effect, and avoidance of 
severe contrasts, in the interests of 
traffic. In regard to low-pressure lighting, 
the ordinary lantern with inverted burners 
and porcelain reflector is still quite an 
efficient device for side-streets. Here 
again the substitution of inverted mantles 
for upright ones, and the use of cluster- 
lights, has proved very beneficial. 
Multiple superheated small mantle lamps 
are becoming very usual for lighting main 
thoroughfares, and are certainly efficient 
and economical in maintenance. They 
are best placed at a fair height of, say, 
15 feet for a. 4-burner unit yielding 
about 350 candlepower (mean of equi- 
distant angular readings in the lower 
hemisphere). The efficiency of high- 
pressure gas lighting in some of the most 
important thoroughfares in London re- 
quires no qualification. Some examples 

of London streets so treated are ad- 
mittedly among the best lighted in the 

The following values of candlepower 
derived from typical lamps may be of 
interest : — 


below horizontal. 

At 50°. 

At 20°. 

" C " upright mantle 

in ordinary street 




No. 4 inverted 

mantle in lantern 

i These 

of same pattern . . 




Two No. 2 super- 


heated burners in 


ordinary street 






Two burner " Keith " 

high-pressure stan- 

dard lamp (nom- 

inal 3,000 c. p.) .. 



Although, as I have remarked, the 
brilliancy of the lighting in certain 
London thoroughfares is probably as high 
as that in any gas-lighted streets in the 
world, and the lighting of London as a 
whole doubtless compares favourably 
with most Continental cities, we should 
not be content to " rest on our oars." 
For interior lighting we have now a far 
wider choice of fittings, reflectors, etc., 
than was available a few years ago. But 
the design of the ordinary street lantern 
has remained substantially the same for 
a considerable time, and little attempt 
has been made to screen the mantle and 
produce a softer and more pleasing effect, 
nor to modify the natural curve of light 
distribution which, with the wide spacing 
inevitable in street lighting, leads to great 
variations in the illumination furnished 
between the lamps. 

At the present time authorities are 
exercising economy and would doubtless 
be disinclined to adopt new and special 
designs that involve greater expenditure. 
But in the future the steady tendency 
towards more scientific and decorative 
methods of outside lighting will be 
resumed. We ought, therefore, now to 
be planning improvements. Much differ- 
ence of opinion exists as to the best 
manner of specifying the illuminating 
power of street-lamps, i.e., whether in 
terms of candlepower at particular angles, 



or minimum illumination furnished in a 
horizontal plane. But it is no doubt 
broadly true that it would be desirable 
to secure more uniformity of illumination, 
coupled with diminution of any tendency 
to glare. Amidst the dark surroundings 
in a street a source which might appear 
only moderately bright against a light 
background is apt to prove glaring. Gas 
lighting is so favourably placed from the 
economical standpoint for public lighting 
that we are apt to neglect the more 
scientific and decorative sides. In the 
main streets of London we might well aim 
at the use of lamp-posts and lanterns of 
a more distinctive pattern — such methods, 
for instance, as the use of multiple-lamp 
standards with sources enclosed in light- 
diffusing globes. Again, assuming that 
suitable heat-resisting glassware is avail- 
able, why should we not design internal 
" diffracting " devices for the purpose of 
altering the distribution of light, such as 
are commonly used with electric sources ? 
If this were done we should doubtless be 
able to provide minimum illumination 
values well above those existing at present, 
even in the most brightly lighted streets. 

Something more might also be done to 
develop decorative and imposing forms of 
bracket and pillar-lights for use outside 
buildings of architectural distinction, 
such as would act as an excellent adver- 
tisement for gas, and would be most 
valuable in yielding additional diffused 
illumination in important streets. As a 
general principle I would suggest that 
such units, being placed at a relatively 
low level, be furnished with diffusing 
glass, both with a view to avoiding glare 
and showing up the design of the lantern 
in a more effective way. 

Gas might also be applied more 
extensively to the spectacular and adver- 
tisement field of lighting, e.g., in illumin- 
ating, by means of concealed lamps, signs 
and bill-boards, etc. 

A feature during recent years has been 
the development of local " parade " 
lighting, or special external lamps outside 
shops, the cost of which is borne by 
tradesmen on the frontage illuminated. 
In Croydon we use both six and eight- 
light low-pressure lamps and 1,000 — 1,500 
(" nominal ") candlepower high-pressure 
lamps. The. position of such lamps 
naturally depends on the frontage. As 

such lamps are very often used for the 
joint purposes of attracting attention and 
illuminating the interiors of windows, 
heights of 8 1 to 10 feet are usual. Some 
tradesmen prefer fitting these lamps with 
parabolic reflectors, thereby using them 
solely for window lighting, and having 
" top " lamps well above the fascia for 
outside display and advertisement lighting 
— a very good scheme. 

I am aware that stress has been rightly 
laid by experts on the prejudicial effect 
of glare from very powerful unscreened 
lamps, at a relatively low level. It is 
much to be desired that tradesmen should 
be led to appreciate the advantages of 
methods of lighting that are free from 
glare, and in cases where lamps are used 
at a low level suitable methods of diffusing 
the light should be encouraged. In this 
connection I may mention that we are 
now giving a test to the latest type of 
silica high-pressure lamps, as the use of 
this form of glassware should prove most 
helpful in overcoming glare. We have 
also, of late, developed top-lighting, well 
above the window level, for purely 
advertisement purposes, and are en- 
deavouring to encourage this method as 
much as possible. As already mentioned, 
the distant control of these outdoor 
lamps by a control-cock within the shop 
is an important feature of installations of 
this kind. 

Lighting of Halls, Churches, Schools, etc. 

The lighting of Halls, Churches, Offices 
and Schools, etc., has engaged our serious 
attention. In such cases the range of 
illumination varies between 2 — 3| foot- 
candles. It may be of interest to give 
particulars of a typical case : — 

Hall, 60 feet by 30 feet. 
Walls, tinted pale green. 
Allowance per square foot of floor area 
— 075 candles. 

Lamps provided to satisfy this allow- 
ance — three 6-burner (superheated) with 
No. 2 mantles, circular opal reflectors and 
lower half lightly obscured globes, hung 
down the centre line ; height of sus- 
pension equal to distance apart. 

Resulting mean illumination — 3 foot- 

For purposes of clearness of vision 
intensities of not less than one foot-candle 



should be aimed at, as with an illumina- 
tion of about - 6 foot-candles and less 
the ability of the eye to recognise detail 
rapidly diminishes. Again, further in- 
creases in illumination over about 45 
foot-candles appear to aid our " sharp- 
ness " of vision, for ordinary purposes, to 
but a very small extent. 

In interiors of this type the lamps are 
commonly spaced at a good height above 
the floor, well out of the range of vision, 
but are also appropriately screened as an 
additional safeguard against glare. In 
certain cases lighting units, comprising a 
large number of small mantles are 
mounted in the form of a ring, direct on 
the ceiling, and the products of com- 
bustion are led away upwards through a 
ventilating shaft. The sources thus 
achieve the double object of providing 
light and assisting ventilation. This 
furnishes another example of the great 
value of modern methods of distant 
control, which enable lights to be placed 
very high up, and generally in com- 
paratively inaccessible positions, which 
are decided purely by the consideration 
of securing the best distribution of light. 

Industrial lighting, of course, forms one 
of the most favourable opportunities for 
gas, on account of the many applications 
it possesses for heating in industrial 
processes. Here, again, we must, not- 
withstanding our favourable position, 
move with the times. There is one 
particularly important circumstance to 
be remembered. Whereas in private 
houses no official recommendations in 
regard to the methods and standard of 
illumination exist, the lighting of factories 
has been the subject of much study by 
the Home Office in this country, whose 
Departmental Committee has already 
issued two comprehensive reports, in 1915 
and in the present year, containing 
detailed recommendations. 

These recommendations may be re- 
garded as the preliminary to future 
statutory requirements of adequate light- 
ing in factories, and should be closely 
studied by the Gas Industry. I am 
confident that, by the aid of modern 
developments, gas lighting will be able 
to satisfy such requirements completely, 
provided we apply illuminating engineer- 
ing methods and study factory lighting 
in a scientific way. One factor with 

which these recommendations have been 
concerned is the avoidance of glare. As 
I have shown, we, in Croydon, attach 
great importance to this essential factor 
in good lighting. Each factory presents 
a distinct problem. In such cases, for 
very fine work, local lights over individual 
machines are preferred, and in such cases 
complete screening of the mantle from 
the eyes of the worker is essential. In 
other cases general overhead lighting is 
demanded, and here methods of distant 
control, in enabling lamps to be placed 
high up out of the direct range of view, 
are of great value. 

Another recent development that will 
prove very useful is the use of vitreosil 
glassware, which satisfies the requirement 
in the last Departmental Committee's 
report in regard to proper shading so 
that no incandescent mantle is dis- 
tinguishable as such when viewed through 
the shade. 

Before concluding, I would add that 
there is ample scope for gas lighting, if 
forethought is exercised for the future, if 
we are quick to adapt ourselves to new 
developments, and if the needs of con- 
sumers are scientifically studied. We 
must not be content to satisfy un- 
instructed public opinion, but must 
educate consumers in the principles 
of good lighting by adequate methods of 
publicity, amongst which demonstrations 
of efficient lighting play an important 
part. In our showrooms we have in- 
tentionally arranged for a varied display 
of fittings, and the method of lighting 
adopted in the different rooms itself 
serves as an object lesson in the use of 
semi-indirect and other modern lighting 
devices. We have also arranged side 
by side examples of obsolete and modern 
fittings, and properly shaded and exposed 
mantles, in order that consumers may 
judge for themselves the difference in 

Next, after publicity, comes the 
question of attention to the needs of a 
consumer after his custom has been 
secured. In almost all cases our success 
has been largely attributable to the fact 
that, after completing the installation, 
we undertake the maintenance; and in 
general do everything that we can to 
make the consumer feel that he is getting 
good value for the gas he uses, and that 




we guarantee him against failure or 
deterioration in the original conditions. 

Thirdly, it is necessary to keep abreast 
of progress and to expend patience and 
trouble, both in encouraging consumers 
to discard obsolete fittings when new 
and better types appear, and in studying 
\ ourselves how these fittings can best 
be applied. Gas undertakings, therefore, 
should study illuminating engineering, 
they should have precise knowledge 
of the intensity and distribution of candle- 
power of the lighting units they use, and 
be able to predict the resultant illumina- 
tion so that promise is confirmed by 
performance in the completed installation. 
Further, they should keep in mind the 
principle that what the consumer needs 
is not merely inexpensive lighting, but 
illumination that is adequate and suitable 
for his needs. In the past we have, 
perhaps, been too prone to emphasise 
the cheapness of gas as an illuminant 
and people have come to assume that 
if gas lighting is adopted the costs of 
installation and fittings must be reduced 

to an absolute minimum, to a degree 
really prejudicial to the ultimate results 
obtained from the installation. Ex- 
perience shows that the importance 
attached by the consumer to the quality 
of the lighting provided is much greater 
than was the case a few years ago, and 
he looks to the undertaking for guidance 
and for information on the latest develop- 
ments. This desire for service we must 
foster in every way possible, and future 
success depends primarily on the 
completeness with which we apply 
illuminating engineering methods in the 
gas industry. 

Finally, they should keep in mind the 
indebtedness to the co-operation of my 
assistant, Mr. W. A. Bishop, by whom 
much of the technical data appearing 
in this papei has been compiled, and 
to say how much I appreciate the useful 
educational work he has done in the 
matter of promoting a better under- 
standing of the elements of illuminating 
engineering amongst the members of 
my <taff. 


The Chairman (Mr. F. W. Goodenough), 
in opening the discussion, added the 
thanks of the members to those of 
Mr. Sandeman to Mr. Bishop for the 
work he had done in assisting to prepare 
the paper, and for having presented it 
in the much regretted absence of Mr. 
Sandeman, who they all hoped would 
be speedily restored to good health. 

Mr. A. E. Broadberry said that the 
considerable amount of ground covered 
in the paper made it somewhat difficult 
to select points for discussion, and he 
regarded it rather as a contribution 
serving as a permanent source of reference. 
It afforded ample evidence of the many 
excellent schemes used by the Croydon 
Gas Company in preparing plans of 
lighting installations, and the most 
important lesson it contained was the 
desirability of treating illumination on a 
scientific basis. He was afraid that 
gas engineers were sometimes too apt 
to be satisfied with existing runs of 
piping instead of trying to improve 
on them. The lighting of buildings 
could often be carried out in a more 
scientific way if architects would 

utilise the advice of experts on illumi- 

The photographs included some 
excellent installations, but he thought 
it should be made clear which were 
taken by artificial light and which by 
daylight. In general it was better to 
take such photographs exclusively by 
the light furnished by the gas lamps, 
as they then gave a picture of the actual 
conditions secured.* 

He was glad to have an opportunity 
of expressing his appreciation of the 
paper and of the considerable amount 
of information it contained. 

Mr. A. Cunnington expressed his 
appreciation of the contents of the paper 
and the evidence it afforded of progress 
in gas lighting. It was encouraging 
to find illuminating engineering being 
applied by a gas company, and the 
furnishing of polar curves for units. 

There were several points that struck 
him, looking at the paper from the 
standpoint of a railway lighting engineer. 

* By the courtesy of Mr. A. E. Broadberry 
we are able to reproduce two excellent photos of 
gas lighting in North London, taken exclusively 
by artificial light. 



Fig. 1. — Outdoor Shop Lighting at Enfield, comprising 13 Keith 600 c.p. high-pressure 

silica cup lamps. 

Fig. 2. — Outdoor Shop Lighting at Tottenham, comprising 13 Keith 600 c.p. high- 
pressure silica cup lamps, and one without a parabolic reflector. 

C - 



When he remembered the difficulty 
experienced by his colleagues in the 
railway world in getting even twenty- 
tenths pressure recognised as a reasonable 
demand, it was refreshing to find a 
statement in the paper that twenty-five 
to thirty tenths are needed for the best 

The use of small mantles was an 
important point. These were taken up 
very early by the Great Western and 
London and North Western, and he 
believed the latter standardised these 
small mantles some time before they 
came into general use. The London 
and South Western Eailway had also 
adopted them, in fact, the railways 
had encouraged the development of 
small mantle gas lamps by the manu- 
facturers. The possibility of using one 
standard size of mantle in clusters was 
a great advantage as it enabled different 
candlepowers to be obtained by varying 
the number of mantles, but only one 
size need be stocked. It was, however, 
desirable that there should be greater 
uniformity as regards size. 

The values given by Mr. Bishop for 
the absorption of vitreosil glassware 
did not quite agree with those he had 
determined, but he noticed that open 
bottom cylinders had been tested and 
these hardly gave a fair figure. He 
thought an absorption of 33 per cent, 
was nearer the mark. This type of glass- 
ware was of considerable value for many 
classes of work, e.g., for desk-lighting. 

As regards the height of fittings he 
observed that Shit, and 10ft. were 
mentioned. This was surely too low 
in such cases as street and shop-lighting. 
He had recently seen a drapery store 
in South London where very good 
results were obtained by raising the high 
pressure lamps above the facia, placing 
them well out on brackets, resulting 
in a material improvement of pavement 
and window illumination. 

He wished to express his appreciation 
of the polar curves showing the efficiencies 
of complete fittings. It was, however, 
necessarv to draw a distinction between 
values obtained with the aid of con- 
centrating reflectors, and values obtained 
from the bare mantle, in making com- 
parisons between different systems of 

He was especially pleased to note the 
emphatic remarks of Mr. Sandeman 
on the subject of the avoidance of glare, 
which illustrated the enterprising out- 
look of the Croydon Gas Company. 

Fig. 1. — Showing method of lighting clock on 
Esher station. 

Fig. 2. — Showing lighting of new booking hall 
at Guildford station by semi -indirect methods. 

Consumers should be taught that glare 
was not only harmful, but wasteful, 
and in railway lighting they had to make 
constant efforts to impress this point 
on people. 



In connection with special railway 
fittings Mr. Cunnington exhibited a 
Sugg lamp of weatherproof design with 
inverted mantle which had been in use 
for several months for platform work. 
A good feature was the screening of the 
mantle so as to utilise light otherwise 
wasted in a horizontal and upward 
direction, but at present the distribution 
of light was somewhat concentrated, 
and it was hoped to get a more 
" extensive " curve which would better 
suit the usual platform spacing. Mr. 
Cunnington also exhibited a slide showing 
the concealed lighting of supplementary 
signals at Wandsworth Town Station, 
which had recently been described in the 
official organ,* and a second slide showing 
the lighting at Esher Station of the two 
sides of a clock by gas lamps concealed 
from view between two overhead girders. 
The lamps also served to illuminate 
the staircase immediately below them. 
At this and other stations effective use 
was made of the distance control valves 
mentioned in the paper. 

A final illustration showed the lighting 
by semi-indirect methods of the new 
Booking Hall at Guildford Station. He 
wished to express his appreciation of 
the kindness of Mr. Dow in taking these 
photographs — the last two under some- 
what disadvantageous circumstances, in- 
volving an accident to the camera 
which broke the ground glass focusing 
screen, and the presence of a very foggy 
atmosphere at Esher. 

Mr. A. H. Stevens (London and 
North Western Railway) pointed out 
that Mr. Sandeman spoke of present- 
day gas as yielding a duty of 20 candles. 
He asked if he might be informed of the 
calorific value of the gas referred to, as 
" present-day " gas showed so much 
variation that " average " gas was rather 
difficult to define. He stated that on 
the London and North Western Railway, 
they met with gases varying from 
250 B.Th.U. to 550 B.Th.U. per cubic 

Mr. J. G. Clark. said that he would like 
to express his thanks to the author for 
this excellent paper, and also to Mr. 
Bishop in presenting it in the absence 

* Illum. Eng., Nov., 1921, p. 223. 

of Mr. Sandeman. In regard to the 
question of efficiency he would like 
to see the information given in terms of 
light energy per therm or centi-therm. 
He also preferred lumens per centi-therm 
per hour in preference to foot-candles 
per square foot. 

He wished to emphasise the importance 
of securing mantles of uniform size, 
particularly for cluster lamps. Some 
specification whereby manufacturers could 
provide such mantles within narrow 
limits of variation was of great import- 
ance to the progress of gas lighting on 
scientific lines. 

He entirely agreed with Mr. Sandeman 
in the usefulness of vitreosil, particularly 
for school lighting. This silica was of 
great help for some school work he 
was recently engaged upon where it 
was necessary to provide adequate 
illumination and a cheerful effect. He 
was also in agreement with the figures 
given in reference to the relative 
efficiencies of direct, semi-indirect and 
indirect lighting, except that he would 
like to see them stated in relation to the 
consumption of therms. 

He noticed that Mr. Sandeman referred 
to a top gap in the burner with a view 
to avoiding obscurity overhead. Opal 
glass, if this could be used, would allow 
sufficient upward light. In school 
lighting, where not only the working 
plane has to be considered, it was desir- 
able to allow a little light to go upwards 
in the case of opaque units. 

The intensity of illumination pro- 
posed in school lighting, viz., 3'0 foot- 
candles was, he considered, very satis- 
factory, and was a minimum which 
ought to be aimed at. He also wished 
to express approval of the method 
mentioned as used in the Croydon Gas 
Company's Showrooms, of showing good 
and bad methods of lighting side by side. 
This would be of considerable service 
in educating consumers. 

Mr. S. B. Chandler said the paper 
came at an opportune moment, and 
proved that modern gas appliances are 
available to meet all demands and 
satisfy any lighting problems that arose. 

Undoubtedly, great importance 
attached to a satisfactory system of 
maintenance, and this service appeared 



to represent the best means of retaining 
lighting installations. 

Manufacturers should certainly furnish 
polar curves of light distribution for 
their lamps, both with and without 
reflectors or shades, as information of 
this character would materially assist 
illuminating engineers in the design and 
lay-out of lighting schemes. With regard 
to high-pressure lighting, mention might 
be made of a large factory recently 
erected in South London in the area of 
supply of his Company : the Keith 
system had been installed, about 300 units 
providing a candlepower of approxi- 
mately 50,000 being used. Special 
attention had been paid to the proper 
spacing of the various lamps and suitable 
shades selected to secure even illumina- 
tion throughout the five floors, a value 
of 3'5 to 4"5 foot-candles being provided 
for. The machine shop is well illumin- 
ated with low-pressure inverted lamps, 
each with a cluster of three No. 2 mantles, 
the lighting effect being of the order of 
four foot-candles at machine top level : 
both installations are giving excellent 
service, to the complete satisfaction of 
the workers. 

Mr. W. J. Liberty said he was much 
interested in the paper. It was evident 
that results with superheated multiple 
burners showed a great advance, as 
apparently as much as 40 candles per 
cubic foot was obtained in some instances. 
He might mention that on London 
Bridge clusters of " Kempton's "' ten 
mantles superheated had been recentlv 
adopted ; the consumption was a little 
under 36 feet per burner, and small 
mantles were used. On Blackfriars 
Bridge five - light preheated burners 
were also used. The consumption was 
about 14 cubic feet per hour, somewhat 
similar to London Bridge. There was 
little doubt that the small mantle, 
being more completely filled by the 
flame, gave the best efficiency. As 
illustrating the tendency towards using 
a large number of mantles in a single 
lantern he might mention that he had 
recently seen as many as sixteen mantles 
so used, giving about 1,000 candlepower. 
It was an advantage to be able to replace 
any defective mantle, leaving the others 
intact. In each of these cases, the 

regulator was inside the lamp, so that 
the maintenance man could, by opening 
the door, make the necessary adjustments 
easily and without inconvenience ; 
whereas, if the regulator was at the top. 
it was too hot for him to manipulate. 
With these preheated multiple burners, 
by having small mantles they got a 
mantle really full of flame. There 
seemed to him with this system to be 
no end to the number of burners they 
could get into a lantern. He had some 
centrally suspended across a city 
thoroughfare, containing sixteen pre- 
heated burners in clusters of eight 
burners, with small mantles, giving 
1,000 candlepower, and suspended 26 feet 
above the roadway. Maintenance on 
account of glassware was less with these 
lamps. In his opinion all upright and 
other burners should be scrapped and 
preheated burners should be put in. 
Tin' lighting efficiency was increased with 
a lower consumption. He had been 
much interested in the slides exhibited. 
He was not sure that lighting experts 
would approve the mounting of high 
pressure gas lamps on posts or brackets 
only 8i feet high, but he observed that 
Mr. Bishop had referred to the advantage 
of placing such lights at a higher level 
when consumers could be induced to 
approve this course. 

Mr. A. Blok said that he would be 
glad if Mr. Bishop would explain more 
fully the nature of the candlepower- 
rating adopted. AVere all the values 
in mean horizontal candlepower, or 
in mean hemispherical candlepower unless 
otherwise specified? It was not clear 
that all values given in the paper were 
calculated on the same basis, which, 
for the sake of comparison, was most 

The table comparing direct, semi- 
indirect and indirect lighting was useful, 
but the conditions in which it applied 
should be understood. Apparently, 
it assumed walls and ceilings of average 
tint, and it would be of great utility if 
correction factors could be furnished 
to enable one to make allowance for 
cases in which the surroundings were 
of an exceptionally dark or light tint. 

It also seemed desirable to evolve 
some shorter expression than 5< cubic 



feet of gas per foot-candle per square 
foot of area illuminated." Possibly, 
lumen- hours per therm, or, as Mr. 
Clark had suggested, lumens per centi- 
therm per hour might be substituted. 
There was still a marked tendency to 
attribute too much mystery to the 
lumen which, in reality, was not difficult 
to understand since the total flux of 
light in lumens could be so readily 
determined from the polar curve. A mere 
inspection of a polar curve, though 
useful in enabling distribution of light 
to be studied, gave no adequate con- 
ception of the total flux of light derived 
from a lighting unit, and in the calcula- 
tion of indoor illumination problems 
especially, the flux method is the one to 
be employed. Accordingly, it should 
be the practice to append to each polar 
curve the total flux of light available. 

In conclusion, Mr. Blok added that, 
while suggesting these improvements, 
he wished to express his cordial apprecia- 
tion of the paper, as illustrating the 
readiness of up-to-date gas companies 
to supply detailed data regarding the 
lamps used. 

Communicated : — 

For comparison with the mean candle- 
powers taken at equiangular intervals 
of ten degrees in the lower hemisphere 
given in table presented at the meeting 
referring to clear and silica glassware,* 
I have worked out the mean hemispherical 
candlepowers and the corresponding 
lumen values for the three cases given : — 










Mean hemispherical 





Lumens = 





Loss of light per 






ft. per hour 




Lumens per cub. ft. 

per hour 




* A slightly amended version of this table 
is presented in Mr. Sandeman's reply to the 
discussion (p. 35). 

The Chairman said that he had the 
same feeling as one or two speakers — ■ 
that attempting to discuss the paper 
was rather like discussing an encyclo- 
paedia. They were indebted to Mr. 
Sandeman for giving them this com- 
pendium of information with regard 
to gas lighting. He was rather interested 
to hear their railway friends' references 
to the question of pressure. Mr. Cunning- 
ton seemed to think that there was some 
inconsistency between Mr. Sandeman's 
pressure and the position taken up by 
the gas industry when it came to a 
question of legislation. He (Mr. Good- 
enough) would just like to say, on this 
point, that what the gas industry was 
contending against in that case was the 
penal minimum pressure at any point 
in the area of distribution, which was a 
different thing from the general working 
pressure in the district. To be asked to 
give a minimum pressure, with penalties 
attached, in a pipe of any size, and at the 
consumers' meters, was a different matter 
from giving such pressure in the mains and 
services as would give consumers an 
adequate supply of gas. The railway com- 
panies or other consumers would have no 
reason to complain of the result of the 
provisions made in regard to gas pressure 
under the legislation as it stood. He 
could only say, as had been said on many 
occasions before, to their friends the 
railway companies, that every gas under- 
taking worthy of the name desired to 
give to the consumers the pressure which 
would enable the consumers at all times 
to get the best out of the gas supplied. 

Reference had been made to the 
candlepower efficiencies given in the 
paper as if they were the maximum 
efficiencies on the polar curves. This 
was not as he (Mr. Goodenough) accepted 
it. He thought the figures referred to 
the mean hemispherical candlepower. 
He also emphasised the great importance 
of educating consumers to purchase only 
burners and mantles of satisfactory 
quality. So-called cheap burners and 
mantles were among the worst enemies 
of gas lighting ; and it was important 
that the men in the gas industry should 
do all they could to educate consumers 
to the true economy of purchasing good 
burners and mantles and particularly 
of placing the renewal of mantles under 



maintenance direct with the gas suppliers. 
Mr. Sandeman also showed that the cost 
of maintenance was lower with a large 
number of small mantles, with the super- 
heater burners, than with the smaller 
number of large mantles and burners 
of the older type. 

Reference had been made to the 
mercurial seal distance lighting for 
groups -of lamps. The Gas Light and 
Coke Company put the system in at 
Victoria Station many years ago — 
perhaps 12 to 15 years — and it had 
worked absolutely satisfactorily. It 
effected a considerable economy to be 
able to regulate the lights according to 
the requirements of traffic. He also 
emphasised the importance of seeing 
that promise was confirmed by perform- 
ance, whether the installation was by 
gas or electricity. The best way to get 
the confidence of the consumer was to 
be sure that he was given something 
better than was promised. Mr. Stevens 
asked about the average present-day 
gas and he (Mr. Goodenough) thought 
the best answer was given by Mr. Clark — 
the efficiency per 1,0C0 B.Th.I'. 

Mr. Leon Gaster said that he wished 
to associate himself with the Chairman's 
expression of thanks o Mr. Sandeman 
and Mr. Bishop for the trouble they had 
taken in preparing the paper, which 
showed how much had been done to 
improve the efficiency of gas lighting 
during recent years. One could not 
but be struck by the ingenuity exempli- 
fied by some of the latest types of fittings 
which enabled many lighting problems 
to be solved in substantially the same 
manner as when electric lighting was 

What, however, was particularly 
gratifying to him was the whole-hearted 
way in which Mr. Sandeman and Mr. 
Bishop had emphasised the value of 
illuminating engineering methods in the 
gas industry. No doubt their experience 
in Croydon had fully justified the effort 
required in obtaining polar curves and 
other data relating to gas lamps, which 
enabled the actual illumination provided 
in" an installation to be determined 
beforehand. He also appreciated the 
recognition, expressed in the paper 
and in the Chairman's remarks, of the 

necessity of assisting the consumer in 
every possible way, and in enabling him 
to get the best results from the gas 
supplied. Their experience in the 
Illuminating Engineering Society had 
always encouraged the belief that there 
were ample opportunities for all illum- 
inants provided, as Mr. Sandeman had 
remarked, that they kept abreast of the 
times by applying the latest illuminating 
engineering methods. 

They all regretted Mr. Sandeman's 
unavoidable absence through indisposi- 
tion, but he wished to congratulate his 
assistant, Mr. Bishop, on the manner in 
which he had presented the paper, and 
on the evidence it afforded of the keen 
interest that was being taken in illumina- 
tion by the younger generation in the 
gas industry. 

Mr. P. J. Waldram (communicated) : 
It is with great regret that I have been 
compelled to lose the opportunity of 
being present at the reading of the paper, 
which forms a notable addition to the 
available data on gas lighting. 

I notice that the author gives data 
on candlepower per cubic feet of gas 
per hour based on 25 and 30 tenths 
pressure ; he also mentions " 14 candle " 
gas and consumption on " modern low 
pressure." It would be valuable if the 
latter term were clearly defined and 
some indication given to enable the 
lighting expert to arrive at the probable 
average pressure for town mains, so 
that he can calculate the drop between 
the mains and the lighting point and 
vary his estimate accordingly. There 
are probably few installations of moderate 
size which can stand the expense of a 
gas engine and blower to obtain the 
more efficient high power gas, and pre- 
heating in bulk, except for furnace 
work, is, I believe, unusual. In general, 
therefore, the illuminating engineer is 
dependent on the town's mains pressure. 

As one who has had to utilise both 
gas and electricity it would appear that 
there is little to choose between them, 
each advance in the one method being 
followed by a corresponding economic 
improvement in the other. Except where 
local prices are abnormal it would appear 
that gas is to-day the cheaper illuminant, 
especially for large installations where 



high power cluster lamps are used. 
This is probably due to the fact that 
multiple mantles, in addition to super- 
heating devices, mutually aid each other 
by heating, with a corresponding rise in 

The lighting expert, however, must be 
sure of his data. In addition to data 
for cluster mantle lamps he should have 
polar curves of single mantle and double 
mantle lamps ; and he must be able to 
get his mantle renewals at reasonable 

I would, therefore, venture to suggest 
that gas companies should not be content 
with developing business that naturally 
accrues to them. Let them pool their 
research facilities. Let every gas fitting 
and shade in the market be measured 
and tested and the polar curve published 
authoritatively as soon as it is available, 
with long period tests at various pressures. 
Unless gas establishes its economic 
advantages it cannot expect professional 
men to dig out the necessary data by 
individual research. 

Mr. A. E. Fry (Plaissetty Manufactur- 
ing Company), communicated : As one 
interested in the manufacture of gas 
mantles I should like an opportunity 
of adding a few remarks on the points 
raised by Messrs. Clark and Cunnington 
with regard to the size of mantles. If 
anything approaching uniformity in the 
size of mantles is to be attained, it is 
essential that the nozzles of lamps- and 
fittings should be standardised, and 
that lighting authorities should insist 
upon standard fittings. At the present 
time there are three different sizes in 
medium rings, with very little variation 
between them, which have been called 
into existence to give satisfactory fittings 
for the differing nozzles put on the 
market by different burner and lamp 
manufacturers. Each type of ring re- 
quires a variation in the manufacture 
of the gas mantle to be mounted upon it, 
thus giving rise to the difficulty in 
obtaining uniform shapes as well as 
causing confusion both to the public 
and to the trade who have to cater for 
their needs. 

It therefore seems desirable that some 
steps should be taken to remedy these 
difficulties if this size unit is to become 

more popular. One size, preferably the 
plain lug ring, might be adopted, and 
standard sizes set up for both rings 
and nozzles, making due allowance 
in each case for shrinkages in manufacture. 

Mr. W. J. Jones (communicated) : 
In the first place I should like to offer my 
congratulations to the author for having 
prepared such an interesting paper. 
It must be almost an epoch-making one, 
for it is the first occasion on which such 
full information on gas lighting has been 
presented, and I feel sure that this data 
will be of special service to illuminating 

I have been greatly interested in the 
progress that has been made in recent 
years in gas lighting, but there are 
one or two points that seem to deserve 
more attention. Throughout the paper 
there are various references to the 
" performance " of gas, and this is given 
in terms of candlepower per cubic foot. 
This seems a somewhat loose method of 
specifying an important quantity, for the 
candlepower is presumably dependent 
both upon the calorific value of the gas 
and the pressure at which it is used. 

Moreover, it would seem desirable 
for the mode of expressing candlepower 
(whether as mean horizontal, mean 
hemispherical or mean spherical) to be 
more clearly indicated. It would add 
greatly to the value of the paper if 
mean spherical or average candlepowers 
for the units were given in order that 
mantles of different shape may be more 
accurately compared. As an example 
of this may be mentioned the table on 
p. 14, where the average candlepower 
is given between 10° and 90° below the 
horizontal. A further point that strikes 
me is, that although pressure of gas is so 
important it is apparently left to the 
consumer to install service governors. 

Mr. A. J. Whyte (Messrs. Jas. Keith & 
Blackman, Ltd.), communicated: We 
were sorry that circumstances prevented 
our being represented at the meeting, 
and we would like to congratulate Mr. 
Sandeman on the excellence of his paper, 
and to put on record our appreciation 
of the timely appearance of this literature 
in drawing attention to what gas can do 
in illumination. 



Of course, to us the reference to high 
pressure gas is of great interest, and there 
is, perhaps, no one more qualified to 
speak of the excellence of high pressure 
gas from the point of view of illumination 
than Mr. Sandeman, as anyone who is 
passing through Croydon after dark will 
appreciate. If evidence is wanted of 
the value of high pressure gas fighting, 
both from the Gas Company's standpoint 
as well as that of consumers, a visit 

Mr. Sandeman deserves well of the 

As an example of one of the latest 
developments in gas lighting, it is of 
interest to refer to a rubber factory at 
Barking, in certain portions of which 
there is a vast amount of French chalk- 
in the atmosphere. Without special 
arrangements no incandescent gas light. 
high or low pressure, could live in such 
an atmosphere. It was accordingly 

Fig. 1.— Showing effect of Keith," duct system " of light in a rubber factory where the 

atmosphere is saturated with dust. 

N.B. — Before taking this photo, the dust was allowed to settle. 

to the districts covered by the South 
Metropolitan Gas Company and the 
Croydon Gas Company will convince 
any impartial observer. There is nothing 
finer to be seen anywhere. 

We are glad to say that both in the 
field of what is known as Scale and 
Parade Lighting, and Factory Lighting, 
business in high pressure gas is still in 
great demand, if not up to pre-war 
standard yet. We would recommend 
Mr. Sandeman's paper to all who are 
anxious to make progress in gas lighting. 

decided to employ the " duct " system 
mentioned in Mr. Sandeman's paper, all 
the air used by the burners being sup- 
plied from outside the building. Instead 
of fitting each burner with its own 
injector, a main pipe is used, which 
carries the fully aerated mixture at an 
extremely low pressure and points are 
taken off at intervals, where the mixture 
is burned in a simple form of fitting. 
The main pipes are divided into eight 
sections, each carrying from five to six 
lamps of 300 c.p. each. 



A small air duct is run across the 
centre of the room near the roof and is 
connected by a chimney to the outside 
air. A special injector connects each 
section of the main pipe into this duct 
in such a way that all the air required 
for the mixture is drawn from the duct. 
Suitable arrangements for controlling 
each line of pipe are made on the duct 
and facilities are provided for removing 
nipples, for cleaning, etc. Adjustment 
of the mixture for any line of pipe is 
made at the injector. 

with dust, or where it is desired to use 
small units, all troubles due to smallness 
of nipple being entirely overcome. 
The only drawback — usually not an 
important one — is that lamps must be 
lighted and extinguished in lines. 

Mr. L. M. Tye (communicated) : It is 
very interesting to read in Mr. Sande- 
man's paper the exacting manner in 
which the Croydon Gas Company con- 
duct the illuminating engineering side of 
their business, and I should like to 

Fig. 2. — A view of the same factory. Photograph taken without allowing dust to 
settle, showing the exceedingly difficult conditions. 

A feature is the volume of mixture 
that can be carried by a comparatively 
small pipe. The mains consist of 1 in. 
pipes of about 120 ft. in length and 
downstems of £ in. pipe — practically the 
same size as would be used with the 
ordinary method of lighting. 

Considering the adverse circumstances 
the lighting has been highly satisfactory, 
and consumption of mantles has not 
exceeded the normal. This system seems 
to have great possibilities in cases where 
the atmosphere of a factory is clogged 

emphasise that the general application of 
such methods would be of great benefit 
to the gas industry. 

In Church lighting, for example, I 
recall an installation made by the Gas 
Light and Coke Company (see p. 33) 
where vastly improved results were 
obtained by the use of prismatic glass 
reflectors of the extensive type which 
were attached to their existing chandelier 

Another excellent example of gas 
lighting on scientific lines is the big 



school at Haileybury, where 16 in. 
Holophane Reflector Hemisphere Units 
are employed in conjunction with 300 c.p. 
high power low pressure burners, with 
the results shown in the enclosed photo- 
graph (see p. 33). 

As another further example of such 
scientific methods, I may mention a boot 
factory in Northampton. Here, by using 
industrial type local gas units (prismatic- 
aluminium covered) it was possible to 
considerably raise the standard of gas 
lighting, an illumination of 12-16 foot- 
candles being provided. 

Mr. W. J. Saxdeman (in reply) : I 
was very pleased to hear of the interesting 
discussion which followed the reading of 
the paper by Mr. Bishop. I was, unfor- 
tunately, unable to be present at the 
meeting but am in full agreement with 
the views expressed by Mr. Bishop. 
There are, however, several points raised 
in the discussion on which some further 
comments may be made. 

Several speakers referred to the im- 
portance of pressure, in which I concur, 
and this point was emphasised in the 
paper. Unfortunately, this matter does 
not rest entirely with the gas company. 
In some districts houses are apt to be 
equipped with unduly small pipes, 
especially where cheapness is made the 
paramount consideration, and in such 
cases pressure at a burner may fall below 
the requisite standard although the value 
supplied at the Company's mains is 
ample. Gas Companies should, therefore, 
make every effort to ensure that those 
responsible for the installation allow 
adequate size of pipes — in cases where 
this duty is not undertaken by them. 

I am glad to see the general endorse- 
ment by Mr. Cunnington and others of 
the value of the small mantle. I quite 
agree with Mr. Fry's remarks regarding 
the desirability of standardisation, and 
any influence which the Society can bring 
to bear in this direction will be welcome. 

Mr. Waldram refers to the need for 
figures for single as well as cluster units. 
Naturally we have available polar curves 
for such units ; while cluster units are, as 
explained, much more efficient than units 
of similar candlepower using fewer and 
larger mantles, the difference in efficiency 
between a cluster small-mantle unit and a 

single small-mantle unit of similar type 
and equipped with superheater is not so 
marked ; some advantage is doubtless 
gained in increased temperature and 
light reflected from neighbouring mantles 
in cluster units, but probably a certain 
amount of light is also absorbed by 
mantles coming in front of each other. 

Reference was made to the meaning of 
" average present-day gas." Mr. Good- 
enough, I believe, referred to this matter 
in general terms, and, as Mr. Bishop 
mentioned, particulars of the calorific 
value of gas used accompanied the polar 
curves presented at the meeting. 

This leads me to refer to the question 
of stating efficiencies in terms of" therms " 
rather than " cubic feet." The sugges- 
tions of Mr. Blok and Mr. Clark on this 
point are doubtless technically correct, 
but in the preparation of the paper I was 
anxious to avoid introducing complica- 
tions and to present matter in a simple 
form, without entering into this somewhat 
debatable problem. Mr. Bishop accord- 
ingly sought rather to present information 
in a form readily understood by the 
" rank and file " of the gas industry. 
However, in what follows we give some 
values expressed in candle-hours per 
" centi-therm " (candlepower being, as 
already indicated in the paper, calculated 
as the mean of equidistant readings in the 
lower hemisphere) : — 

Candle-hours per 
" centi-therm." 

" C " Burner . . . . 29 

Inverted Burner . . 43 

No. 2 Cluster (superheated) 64 

High Pressure (Keith) . . 97 

The drawback to calculations in terms 
of lumen-hours per centi-therm, as sug- 
gested by Mr. Clark and Mr. Blok, 
appears to be that a few B.Th.U. differ- 
ence in the quality of the gas do not, in 
fact, make any noticeable difference in 
the luminosity of the mantles. We 
register gas in terms of cubic feet. 
Assume, for example, that a 4-light lamp 
consumes 10 cub. ft. per hour at 25/ 10th 
pressure, and that the measured gross 
calorific value of the gas is 484 B.Th.U. 
We are thus supplying 10 x 484 = 4840 
B.Th.U. per hour, i.e., 4 - 84 centi-therms. 
If the mean duty of the lamp in the 
lower hemisphere is 350, we shall obtain 



Pig. 1. — A recent installation with Holophane reflectors in a Church in the Gas 
Light and Coke Co's. district. 

:FlG. 2.— Showing the lighting of the " Big School " at Haileybury College with 
16 in. Holophane Reflector Hemisphere Units used with 300 candlepower 
low-pressure burners. 



350 x 2 x 3-142/4-84 = 454 lumen-hours 
per centi-therm (approx.). 

Now this is the point. This 484 gas 
is very likely sold as 470 gas, and people 
making calculations on this basis would 
naturally obtain a different value. More- 
over, quality of gas is not absolutely 
constant and one cannot speak of 
efficiencies in this connection with the 
certainty associated with the never- 
changing electrical watt. Some of Mr. 
Clark's figures were, I believe, based on 
the assumption of 490 gas. Finally, 
there is the question raised above, 
whether a moderate rise in calorific value 
necessarily means a corresponding in- 
crease in candlepower While, there- 
fore, I fully agree that the new method of 
rating in centi-therms well deserves 
study, I think it is premature as yet tc 
present figures on this basis, and I feel 
that the best method at present is to do 
as was done in the paper — give the 
mean candlepower per cubic foot per 
hour, coupled with a statement of the 
pressure and calorific value of the gas 

Next as regards candlepower and 
efficiency ratings. Mr. Cunnington 
pointed out the distinction between values 
obtained for the bare mantle, and results 
for lamps equipped with more or less 
concentrating shades. This, of course, 
should be fully recognised, but with a 
view to convenience in practice I think 
there can be no question that what we 
need is the polar curve of the complete 
lighting unit as actually used. This is the 
information we require in determining 
the illumination to be provided in any 
installation. Such calculations must 
necessarily take into account the light 
inevitably absorbed in the structure of 
the lamp. 

In the final version of the paper we 
have incorporated information indicating 
exactly how the candlepower values are 
calculated from the polar curve. With 
the exception of certain figures for flat 
flame and other obsolete types given at 
the commencement of the paper (obtained 
in days before polar curves were the 
familiar things they are to-day"!), values 
are based on the mean of equidistant 
angular readings in the lower hemisphere. 
I realise that this practice differs from 

the laboratory method, doubtless more 
technically correct, of determining mean 
lower hemispherical candlepower through- 
out, having first ascertained the lumens. 
But here, again, we have a method which 
is readily understood and proves useful 
in practice where one wants to get a 
rapid estimate of the probable average 
illumination in foot-candles that will be 
provided. We have a precedent for this 
method in the tests prescribed in certain 
street-lighting specifications where the 
average of the candlepowers at certain 
angles is measured. With a strict 
point-source the two methods would give 
identical results, and it may be noted 
that in practice we do not apply the 
averaging method to highly concentrated 
units, or lamps giving peculiar polar 
curves, but only to standard types which 
give a fairly uniform distribution of light 
over the working range in the lower 
hemisphere, and where, probably, the 
discrepancy is not very great. It will be 
noted that for this reason - the candle- 
power at 0°, practically negligible, was 
omitted from the calculations, readings 
bein<i taken through the range of 10° to 
90°- — with only one exception, a unit 
used without a reflector. 

It would be easy to calculate results 
in terms of mean hemispherical candle- 
power from the polar curves presented, 
and we would gladly give members of the 
Society who are interested fuller details 
on such points. 

With regard to the figures connecting 
gas consumption and illumination, it is 
now made clear in the paper that these 
refer to units of the ordinary " extensive " 
type (for direct lighting) and that average 
conditions as regards reflection of light 
from walls and ceilings (30 — 40 per cent, 
reflection) are assumed. 

In regard to the effect of vitreosil 
glassware the data in the table presented 
at the meeting were not quite correct, 
and I am accordingly adding an amended 
set of data. As we are here concerned 
with the comparison of the amount of 
light yielded in the lower hemisphere with 
and without the diffusing glassware, the 
mean hemispherical candlepower in the 
respective cases has here been calculated 
and the corresponding absorptions of light 



INDEX, January, 1922. 

Editorial. By L. Gaster 

^Humiliating Enoineeritui Society?— 

(Founded in London, 1909) 

Account of Meeting on December 13th, 1921 
New Members 

Recent Progress in Gas Lighting in relation to Illuminating 
Engineering. By W. J. Sandeman 

Discussion — A. E. Broadberry — A. Cunnington — A. H. Stevens — 
J. G. Clark — S. B. Chandler — W. J. Liberty — A. Blok — 
The Chairman (F. W. Goodenough) — L. Gaster — P. J. 
Waldram — A. E. Fry — W. J. Jones — A. J. Whyte — 
L. M. Tye — W. J. Sandeman (in reply) 

Reviews of Books 

Topical and Industrial Section 




Three No. 2 Superheated Mantles. 

Pressure 25/10 ; Consumption 7-5 cubic 
feet per hour ; Calorific value, 484' 8 
B.Th.U.s {gross). 




Closed Vit- 




reosil Cup 
(side slots). 









































Mean Hem. 






Lumens M.H.S.C, P. 


= 1375 








Z8 /o 


The values thus approximately cal- 
culated are in substantial agreement with 
those given by Mr. Blok. It is of interest 
to mention that if, instead of calculating 
mean hemispherical candlepower, one 

merely takes the mean of the candlepower 
values in each column the discrepancy 
in the three cases would be about 2 per 
cent., 15 per cent, and 3 per cent, 

I am glad to note Mr. Whyte 's refer- 
ences to the high-pressure lighting in the 
Croydon district, and the supplementary 
data he has given on the " duct " system 
for use in dust-laden atmospheres. 

I am also glad to notice the practical 
examples of judicious uses of gas lamps 
on railway stations given by Mr. Cunning- 
ton, and the gcod examples of installa- 
tions described by Mr. Tye. In the 
address at the meeting a number of ex- 
amples, good and imperfect, were shown. 
I should like to make it clear that in some 
cases methods involving some degree of 
glare were intentionally shown as a con- 
trast to more scientific lighting with well- 
screened lamps. As mentioned in the 
paper " uninstructed public opinion" still 
desires a blaze of light in some cases, and 
time is necessary for us to educate the 
public in the desirability of avoiding 





New Holborn Showroom. 

We were recently afforded an oppor- 
tunity of seeing the new showroom of the 
Metropolitan-Vickers Electrical Co., Ltd., 
at 232-3, High Holborn. 

Six rooms on the ground floor are de- 
voted to fittings, an interesting feature 
being the long series of windows at right 
angles to Holborn, as well as the main 
window in this street. Here lighting 
fittings in distinctive styles and great 
variety may be seen, one of the most 
effective items being the room executed 
in the style of William and Mary. A 
section is also given up to other domestic 
applications of electricity, such as kettles, 
irons, etc., and cooking ranges, one some- 
what novel exhibit being an electric 
motor-driven apparatus for laundry work. 
A number of electric radiators were also 


Messrs. Alrae & Co. (13, Haverstoek 
Hill, N.W. 3) send us particulars of the 
" Gemlite " burner, stated to be the 
latest and smallest type of inverted gas 
burner on the market. It is rated at 
the high efficiency of from 16 — 20 
candlepower per cubic foot and at a 
low consumption of - 9 cubic foot per hour. 

The burner is of solid construction, the 
stem parts being turned from the solid, 
and the gallery is fitted with an aluminium 
heat deflector, which always remains 
bright and does not corrode. 

The inverted mantle used with the 
" Gemlite " burner is less than half the 
size of the standard bijou, and the fabric is 
of artificial silk (soft not collodionised); 
this type of mantle being preferred as 
giving more illumination and longer life, 
and ensuring a sound mantle when first 
lighting up. The " Gemlite " is specially 
recommended for use in cases where 
only a small light is needed. 


The Electric Lighting of Shop-windows. 
By G. K. Fletcher. (Benn Brothers, 
Ltd. 1921. Is. pp. 38 ill.) 
This little publication illustrates the 
tendency towards specialised booklets on 
various aspects of illumination. The 
author deals with shop-lighting in a 
simple and practical way the matter 
being divided into seven chapters. After 
a brief analysis of the objects of window- 
lighting, there is an explanation of 
common electrical terms and a table 
illustrating the calculation of units con- 
sumed. The author then embarks upon 
a more detailed discussion of various 
aspects of shop-illumination, and we are 
glad to see that a caution is given against 
the display of bright, unscreened sources 
in the line of vision. In general, the 
author avoids the use of technical terms, 
though on the last page a recommenda- 
tion of 10 — 20 foot-candles is given. We 
would suggest that in a subsequent 
edition this term should be more fully 
defined and that a little more specific 
information on the relation between 
illumination and consumption of energy 
might be given. A feature is the use of 
bold black and white sketches to illustrate 
various lighting arrangements. 

The Electrical Engineer's Diary and Year 
Book. (1922. S. Davis and Co., 31, 
St. S within* 8 Lane, London, E.CA. 
536 pp.) 

The edition of the Electrical Engineer's 
Diary for 1922, the fourteenth year of 
publication, has as usual been consider- 
ably revised. The section on Applications 
of Electricity now covers wide ground, 
such different propositions, as the use of 
electricity in connection with agriculture 
and welding, organ-blowing and hair- 
dressing, now being dealt with. As in 
former years, a considerable space is 
devoted to lighting. A new section has 
been added dealing with Trade Pro- 
motion. This contains, amongst other 
items, a list of electrical show windows and 
central station showrooms, a summary 
of the conditions of sale of goods in the 
United Kingdom, and notes on the 
preparation of tenders. 

We notice that increased printed data 
have apparently entailed some com- 
pression of the " daily space " in the 
diary, but the area available for appoint- 
ments noting should still be ample. 
The Diary has established its position as 
a useful publication to electrical engineers, 
and the present edition appears to be 
well up to the standard of its predecessors. 



illuminating Engineering Society. 

(Pounded in London, 1909.) 



Tel. No. Victoria 5215. 


The Use of Light as an Aid to Aerial Navigation. 

The Paper read by Lieut. -Colonel Blandy at the meeting of the 
Illuminating Engineering Society on January 31st proved both opportune 
and interesting. On many occasions the Society has dealt with problems 
affecting traffic, but this meeting was devoted to lighting in connection 
with the latest stage in transport, namely, aerial navigation. 

Following the precedent set at former meetings, when topics of common 
interest to other bodies have been discussed, the co-operation of the Royal 
Aeronautical Society in a joint meeting was invited. The Society had also 
the privilege of the presence in the chair of General Sir Frederick Sykes, 
Controller-General of Civil Aviation, who has done so much for the develop- 
ment of aircraft, and for the encouragement of civil aviation in particular. 
General Sykes, in opening the discussion, pointed out the great importance 
of proper artificial lighting as an aid to flying by night. The great advan- 
tage of aerial traffic is the high speed attainable. But on journeys of 
moderate distance this advantage may be lessened or even neutralised, 
if aircraft have to lie idle at night, and cannot, like railways and motor- 
cars, carry on when daylight has disappeared. In winter, especially, 
when daylight is so restricted, inability to fly safely by night would be a 
serious drawback. 

The proper use of artificial light in connection with aerial navigation, 
therefore, is one of the most important problems, on which its future largely 
depends. Little has been published on this subject hitherto — indeed, we 


believe that Colonel Blaridy's Paper is the first attempt to give a general 
review of the varied problems involved. We have first the use of light on 
aircraft ; second, the use of light at aerodromes ; third, the construction 
of aerial lighthouses. Lights carried by aircraft serve different purposes. 
The International Convention has specified the nature of the " navigation 
lights." In view of the high speed at which aircraft now travel these 
need very careful design, and the author suggested that possibly increased 
range might be found necessary in the future. Here we meet the familiar 
problem already discussed in connection with motor headlights — the 
reconciliation of sufficient intensity with absence of glare. The Convention 
recommended that "navigation lights must not be dazzling." In view 
of the fact that aircraft often travel in dense darkness this condition may 
not be easy to meet. 

The lighting of the quarters for passengers and crew on board aircraft 
is also a somewhat vital matter. Perhaps the most important consideration 
is the increased feeling of security that adequate lighting of the saloon 
occupied by passengers affords ; in the future, we have no doubt, lighting 
will be such as to enable passengers to read and write with the same facility 
as on a railway journey. 

Aerodrome lighting also presents quite a variety of aspects, including 
the use of lights to indicate the presence of obstructions (aerial masts, 
buildings, etc.) and the lighting of the actual ground of the aero- 
drome. Here, curiously enough, one meets with expert views somewhat 
resembling those expressed by shipmasters in the discussion on ship-lighting 
last year. The view was then expressed that artificial light on the deck 
of a sailing ship was not desirable. Similarly one speaker was inclined 
to think that actual lighting of the surface of the ground of an aerodrome 
was not of great assistance, though the marking out of safe alighting areas 
by means of isolated lights was agreed to be highly necessary. It is evident 
that ground-lights in general need to be arranged with extreme care in 
order to avoid dazzling of aviators or confusing shadows. Some of the 
devices referred to in Col. Klandy's Paper, and in the course of the 
discussion, have evidently been designed in a highly scientific manner, 
and should help towards the solution of these problems. 

One of the most interesting sections of Colonel Blandy's Paper was 
that dealing with aerial lighthouses (which indicate the route to distant 
travellers) and local pilotage lights (which act as a guide to aviators when 
approaching their destination). The design of both classes of lights has 
evidently been studied with great care, and the data on range indicate that 
considerable progress has been made beyond the conditions met with in 
early lighting devices. One of the most important considerations is 
homogeneity of light within 180 , such that the light shall appear equally 
distinct to aviators at all angles. It is this feature that marks the great 
distinction between the ideal aerial lighthouse and the marine lighthouse, 
though it is interesting to observe that the latter have proved of great 
service to aerial traffic. 

Finally, there are the numerous problems involved in the use of special 
landing lights, luminous signals, etc., on which much remains to be done. 
A number of problems awaiting solution were brought forward in the Paper, 
and also in General Sykes' remarks from the Chair ; these will no doubt 
receive attention from members in a position to give useful service. Colonel 
Blandy has contributed a paper which should prove of historic and 
permanent interest. 


The Influence of Mist and Fog on Visibility. 

Aerial navigation is naturally affected to a great degree by atmospheric 
conditions, the presence of fog and mist in particular interfering with 
regularity of service. Meteorological experts have rendered most valuable 
service in affording information of climatic conditions likely to be 
encountered en route, and this branch of scientific study has become an 
essential supplement to the air service. 

The problem of the effect of atmospheric conditions on visibility has 
various aspects. Aerial lighthouses, navigation lights and luminous signals 
are apt to be obscured by mist and fog, and the problem of countering 
its effects is a very difficult one. There has been much discussion as to 
the influence of colour of light on penetrating power, and it appears that 
no very definite opinion on this point has so far been reached ; at all events 
the difference in penetrating power is not apparently sufficient to suggest 
that a light suitable for use in a dense fog is likely to be evolved in the near 
future by this means. The visibility of distant solid objects, as compared 
with sources of light, is a somewhat different problem. The veiling effect 
of a luminous mist is referred to in an interesting contribution by 
Dr. J. S. Owens to the report of the Advisory Committee to the Meteoro- 
logical Office (Air Ministry) on Atmospheric Pollution.* Reference is 
also made to the effect of want of achromatism in the human eye, which is 
commonly short-sighted for violet. Distant blue objects (or objects 
illuminated by blue light), therefore, tend to become blurred and indistinct. 
The whole question of the scattering of light by suspended particles in the 
atmosphere is of great scientific and practical importance, and readers will 
find this report of great interest. Much has yet to be learned regarding the 
effect of suspended impurities in the atmosphere in causing absorption of 
light, both natural and artificial, and it is gratifying to recall that the 
Illuminating Engineering Society is co-operating in researches in this field. 
The ingenious apparatus by which the amount of suspended solid 
impurities in the atmosphere at any moment can be determined has yielded 
some interesting results. It appears that the presence of these impurities 
follows a well-defined cycle during 24 hours, and there is evidence that 
they are due in a large measure to the domestic use of coal in the open grate, 
with its accompanying emission of smoke. It is now well recognised that 
smoke-abatement is of great value in lessening the obscurity of mists 
and fogs in the neighbourhood of large cities, and in a moist atmosphere, 
such as prevails round these islands, the effects of these impurities may be 
far-reaching. We hope that the Committee will continue its useful work 
which may lead to most beneficial results in the future. 

* Report of the Advisory Committee to the Meteorological Office (Air Ministry 
Atmospheric Pollution, M.O.249, 1922 (published by H.M. Stationery Office, Imperial House, 
Kingsway, London. 2s. iid. post free). 

B 2 


The Development of Floodlighting. 

Floodlighting, involving the illumination of the frontage of a building, 
or any large area such as a sign, by concealed projectors, has for some time 
been a familiar process in the United States and on the Continent. In this 
country the restrictions imposed by the war checked its development, 
and it is only recently that its possibilities have been utilised to any great 
extent. In this issue (pp. 65-68) we are giving particulars of several installa- 
tions by leading makers of lamps and lighting appliances. The results are 
quite hopeful, and it may be anticipated that the system will make further 
progress. From the illuminating engineering standpoint there is much to 
be said for the method. Its primary merit is that the lamps are concealed 
from the view of the observer. It seems capable of striking and artistic 
results, and there is no doubt that the diffused light reflected off the surfaces 
of buildings, etc., is an ai^ to street-lighting, whereas the exhibition of 
unscreened powerful lamps at a low level may prove a menace to traffic. 
Floodlighting, in short, is a development of spectacular lighting on similar 
lines to the use of concealed lights for illuminating shop-windows. 

In this country there arc various factors that somewhat hamper the 
application of the method to the illumination of frontages of buildings. 
One difficulty is that buildings that have stood for any length of time 
become coated with soot to a greater degree than probably is the case in 
American and Continental cities. The prevalence of mist and fog, and the 
comparative rarity of a clear atmosphere giving sharp-cut effects, is also a 
limitation. Other restrictions are imposed by structural conditions. 
Some buildings are provided with exterior cornices, etc., which serve as a 
natural position for projectors. Others, destitute of such structures, can 
only be lighted from a distance. Speaking generally, there is little doubt 
that the best effects are obtained when projectors can be stationed a fair 
distance away. Lighting units placed very near to the surface of a building, 
illuminating it very obliquely, are apt to produce confusing shadows and 
distortion of effect. The question arises how far owners of property are 
entitled to utilise, by mutual agreement, the roofs of adjacent buildings as 
stations for projectors. 

Another circumstance which is helpful to floodlighting is the existence 
of a clear view of the building illuminated. The demand for a " brighter 
London " has led to the suggestion that buildings along the embankment 
should keep their blinds up so as to exhibit their lights. There seems little 
art in this device. A much more impressive and interesting effect would 
be obtained if the exteriors of certain important buildings could be 
illuminated by concealed lights so as to stand out as bright objects when 
viewed from the other side of the river. 

Finally, we should like to emphasise the importance of co-operation 
between the architect and the lighting expert at an early stage in the 
design of a building, where floodlighting effects are contemplated. 

A problem of special interest is the nature of the shadows cast by 
powerful lights near the face of the building, which may give rise to effects 
quite distinct from those caused by diffused daylight. In some cases the 
effect may be grotesque, but in others, although different from those due 
to natural lighting, they may give a pleasing impression. The sympathetic 
co-operation of architects would do much to encourage the judicious use 
of floodlighting, and the avoidance of unsightly effects. 

Leon Gaster. 





Gbe 3lluminating Engineering Society 

(Founded in London, 1909.) 

The Illuminating Engineering Society is not, as a body, responsible 
for the opinions expressed by individual authors or speakers. 



(Joint meeting of the Royal Aeronautical Society.) 

(Proceedings at the meeting of the Society held at the House of the Royal Society of Arts, 
18, John Street, Adelphi, London, W.C., at 8 p.m., on January 31st, 1922.) 

A meeting of the Society took place 
as stated above, the Chair being taken by 
General Sir Frederick Sykes, G.B.E., 
K.C.B., C.M.G. The Minutes of the last 
meeting having been taken as read, the 
Hon. Secretary read out the name of 
a new applicant for membership as 
follows : — 

Blandy to read his paper on " The Use 
of Light as an Aid to Aerial Navigation." 

The paper was illustrated by a variety 
of lantern slides and diagrams, together 
with some interesting apparatus, includ- 
ing some headlights and a strontium 

An interesting discussion ensued in 

Mr. E. T. Swinton 

London County Council, Public Health Dept. 

The names of applicants announced at 
the previous meeting on December 13th, 
1921,* were read out again, and these 
gentlemen were formally declared members 
of the Society. 

Sir John H. Parsons, the President 
of the Society, then called upon General 
Sir Frederick Sykes to occupy the 
Chair during the discussion, and expressed 
his pleasure at the presence on the plat- 
form of several representatives of the 
Royal Aeronautical Society, with whom 
a joint meeting had been arranged. 
General Sykes then took the Chair and 
called upon Lieut.-Colonel L. F. 

* Illum. Eno., Jan. 1922, page 5, 

which Sir Frederick Sykes (Chairman), 
Colonel Mervyn O'Gorman, Sir 
Sefton Brancker, Sir Acton Blake, 
Mr. Haydn T. Harrison, Mr. T. E. 
Ritchie, Colonel Gold, Mr. P. J. 
Waldram, and Mr. Watson, took part. 
A cordial vote of thanks to Lieut.- 
Colonel Blandy for his excellent paper, 
and to General Sykes for presiding, 
was passed unanimously. The Chair- 
man announced that the next meeting 
would take place towards the end of 
February, 1922, when a discussion on 
Industrial Lighting ; Ideal Requirements 
(legislative and otherwise) and Practical 
Solutions would be opened by Mr. L. 





By Lt.-Col. L. F. Blakdy, D.S.O., H.E. 

(Presented at the joint meeting of the Illuminating Engineering Society and the Royal Aero- 
nautical Society held at the House of the Royal Society of Arts, 18, John Street," Adelphi, 
London, W.C., at 8 p.m., on Tuesday, January 31st, 1922.) 

I propose to deal in this papei with the 
use of light in connection primarily with 
commercial aviation. From a military 
point of view the main object in an area 
of active operations is to be as incon- 
spicuous as possible, and therefor'- to 
restrict the use of light both in aircraft 
and on aerodromes ; in fact, I may say 
one acquired an instinctive dislike for 
light of any kind if one was within reach 
of an enemy projectile of any Bize or 

It will, I think, then be more interesting 
to pursue our subject under peace con- 
ditions when the airman is anxious to 
have as much light as possible for all 
purposes. We cannot, however, pass on 
without reference to one highly organised 
and vast system of lighting used for war 
purposes 1 mean the greatesl display of 
illumination the world has ever seen, 
that of the searchlights in and around 
London whenever there was the least 
chance of a bomb dropping out of the 
skies. You have all seen the magnificent 
display, and many of you no doubl have 
helped in its production. 

Around London itself, but excluding 
the outer barrier, there were about 120 
searchlights ; these varied in size, some 
being 24-inch projectors, some 36-inch, 
and others 48-inch. All these sizes were 
used for both fixed and mobile work, 
though the two larger sizes were really 
unsuitable fur the latter, owing to their 

During the earlier working of the anti- 
aircraft defence, these searchlights were 
run at a low current density, the 24-inch 
lights taking 50 amperes at 50 volts, the 
36-inch lights 150 amperes at 60 to 65 
volts, and the largest lights 190 amperes 
at 70 volts. Various sizes of carbons 
were used, the bulk of those supplied 
being 38 mm. diameter positive and 
20 mm. negative for the 30 and 48-inch 

projectors. At a later date, high in- 
tensity lamps were used to a certain 
extent with current about 150 amperes 
at 65 to 70 volts : these lamps had smaller 
carbons, of course, being fitted with 
16 mm. positive and 11 mm. negative 

For the 24-inch projectors, Crompton's 
automatic lamp was used to a large 
extent ; in the case of the 36-inch, the 
lamps varied to fit the dim-rent makes 
of projectors in use ; in most cases hand- 
feed lamps were used owing to their 
simplicity and ease of manufacture. 

The reflectors were invariably of the 
glass paraboloid type. 

Tilling-Stevens and Dennis-Stevens 
30 k.w. lorries were largely used to supply 
current for the mobile lights, while 24 k.w. 
generating sets direct coupled were used 
for stationary lights. In addition, motor 
generators were utilised — from A..C. single 
2 and 3 phase of various voltages 
and periodicity, to D.C. 80 to 100 volts, 
300 amperes. 

Lights earned on Aircraft. 

Turning now to peaceful flying, we 
will consider first the lights used on board 
aircraft. These can be divided into two 
systems — internal and external lighting. 


As regards the former, which is re- 
quired for working the craft and the con- 
venience of the passengers, we will 
examine the arrangements in R. 36, our 
most modern passenger airship. This 
ship is lit internally with ordinary 12-volt 
metal filament incandescent lamps ; the 
necessary current is derived from five 
generators, one in each of the engine cars. 
Each generator is belt driven from the 
main propeller shaft, and charges a 
floating secondary battery of 40 ampere 



hours capacity; the generators and 
batteries are laid out in two systems, 
those in the four wing cars supplying 
current to the passenger car, control car, 
wing engine car, and internal navigation 
lights. The generator in the stern car 
supplies current to this car, the stern 
navigation light and after corridor lights, 
while all generators are coupled through 
switches and fuses so as to admit of the 
isolation of any one generating unit. All 
cables are run through bonded aluminium 
troughs with loose lids ; switch boxes are 
rendered gas tight by rubber glands over 
the switch handles, and the cable exits 
are sealed in a suitable box and embedded 
in a bitumen compound. The lamps are 
placed in either ceiling-rose or wellglass 
fittings, and are controlled by tumbler 

driven by the main engine will be lifted. 
The D.H. 32, also a new type, will pro- 
bably have a wind-driven generator. 

Lights have been provided for some of 
the navigating instruments in certain 
machines — these are usually 2-volt metal 
filament lamps of 1 candlepower run off 
accumulators. Bristol fighter machines 
are fitted with a wind-driven generator 
and a 12-volt floating battery of 25 
ampere hours capacity, which supply 
current for navigation lights, heated 
clothing, etc. 


With regard to external lighting the 
International Convention for aerial navi- 
gation contains in Annexe D, Section 1, 

S ketch plan of ligh t:. 
5P / on the aircraift 


Fig. 1. 

switches ; all these items are gastight. 
There are 48 lamps of 8 candlepower each 
in the passenger accommodation, the 
control car, power cars and wireless cabin 
being fitted with eight roof lights of 
6 candlepower. Six 3 candlepower in- 
spection lights on flexible leads are pro- 
vided for the control and power cars, 
which have also nine instrument lights of 
1 candlepower. 

In the body of the airship, where are 
situated the crew's quarters and mess 
deck, there are ten lights of 3 candle- 
power. The wiring diagrams of this 
airship are on the wall and may interesl 
some of you. 

One of the most modern British heavier- 
than-air machines which will be actually 
flying for passenger traffic this year is the 
D.H. 34, and provision has been made 
for the internal lighting of this type. 
No details of the lighting have been yet 
settled, beyond the fact that a generator 

" Rules as to Lights," i.e., navigating 
lights to be carried by aircraft. The basic 
principles of these regulations are founded 
upon the International Regulations for 
preventing collisions at sea. 

Dealing first with those lights which 
must be exhibited when an aircraft is under 
way. we find the following rules : — 

the word '" visible " in these rules 
when applied to lights shall mean visible 
on a dark night with a clear atmosphere. 
The angular limits laid down in these 
rules as shown in the sketch (Fig. 1) 
shall be determined when the aircraft is 
in its normal attitude for flying on a 
rectilinear horizontal course. 

1. The rules concerning lights shall 
be complied with in all weathers from 
sunset to sunrise, and during such time 
no other lights which may he mistaken 
for the prescribed lights shall be ex- 
hibited. The prescribed navigation 
lights must not he dazzling. 



2. A flying machine, when in the air 
or manoeuvring on land or water under 
its own power, shall carry the following 
lights : — 

(a) Forward, a white light visible in 
a dihedral angle of 220 degrees, bisected 
by a vertical plane through the line of 
flight, and of such a character as to be 
visible at a distance of at least 8 kilo- 

(b) On the right side, a green light so 
constructed and fixed as to show an 
unbroken light between two vertical 
planes whose dihedral angle is 110 degrees 
when measured to the right from dead 
ahead, and of such a character as to be 
visible at a distance of at least 5 kilo- 

(c) On the left side, a red light so 
constructed and fixed as to show an 
unbroken light between two vertical 
planes, whose dihedral angle is 110 
degrees when measured to the left from 
dead ahead, and of such a character as 
to be visible at a distance of at least 5 

(d) The said green and red side lights 
shall be fitted so that the green light 
shall not be seen from the left side, nor 
the red light from the right side. 

(e) At the rear, and as far aft as 
possible, a white light shining rearwards 
and visible in a dihedral of 140 degrees 
bisected by a vertical plane through the 
line of flight and of such a character as 
to be visible at a distance of at least 5 

(f) In the case where, in order to 
fulfil the above conditions, the single 
light has to be replaced by several lights, 
the field of visibility of each of these 
lights should be so limited that only one 
can be seen at a time. 

3. The rules determined for the light- 
ing of flying machines shall apply to 
airships subject to the following modifica- 
tions : — 

(a) All lights shall be doubled ; the 
forward and aft lights vertically, and 
the side lights horizontally in a fore 
and aft direction. 

(b) Both lights of each pair forward 
and aft shall be visible at the same time. 

The distance between the lights com- 
prising a pair shall not be less than 2 

The fitting of these lights to comply 
with the regulations so as to retain their 
characteristics, presents considerable 
difficulty in practice and is impossible in 
some instances. 

The two pronounced cases are ; — 

(1) In single-engined tractors. 

(2) In airships it is not possible to 
mount the two white lights so that both 
are visible through the entire vertical 

It is possible in certain positions for 
one side light in airships to eclipse the 
other since it is laid down that they shall 
be doubled horizontally. 

How far in actual flying these diffi- 
culties will present any serious dangers 
must be left to experience. Possibly 
those connected with the insurance of 
aircraft will think this is not a very satis- 
factory way of dealing with it, but I can 
assure them that the question has been 
studied in minute detail by the Research 
Department of the Air Ministry, and if 
the regulations can be improved upon the 
matter will be taken up internationally 
at the earliest moment, ft is a point 
on which the assistance and valuable 
experience of the Illuminating Engineer- 
ing Society would be welcome. 

I would like to go a little into the detail 
of the design of these navigating lights. 
You have seen on the diagrams in what 
positions they are to be placed in air- 
craft. Consider now the port and star- 
board lights. We are given by the 
Convention " Rules as to lights " very 
definite limits to the dihedral angle and 
we are given a definite range of 5 kilo- 
metres to be obtained throughout this 

It is obvious that we should eliminate 
any " fringe angle." This elimination 
of the fringe angle can be partially effected 
by screening. 

A screen similar to that used on ships 
for a port or starboard light would be 
the ideal method, but there are diffi- 
culties in designing this screen, the diffi- 
culties of construction and aerodynamics. 
to secure sufficient rigidity and give a 
minimum of head resistance consonant 
with the desired screening effect. 



If the screen is too short we introduce 
the clanger of a fringe angle, allowing the 
beams of the side lights to cross at some 
point ahead in the fore and aft centre line 
of the aircraft. 

Careful experimenting both in the 
laboratory and actually in aircraft has 
led to a design of screen which is a com- 
promise, giving a uniform intensity of 
beam throughout the prescribed dihedral 
angle and limiting as far as possible the 
fringe angle. By means of this screen 
we get a fringe angle of the order of five 
degrees, but the intensity of the beam is 
naturally considerably less within the 
fringe angle. The range of 5 kilometres 
is preserved in the dead ahead direction, 
but in the fringe angle the range is only 
in the order of two and a half kilometres. 

Here on the table is an actual sample 
of a starboard light as fitted to either an 
aeroplane or airship. 

Dioptric lenses or reflectors have not 
been experimented with as a satisfactory 
solution has been found with the screen. 

Another difficulty has been found in 
obtaining the correct formula for the 
tinting of the coloured glasses. The usual 
signal red and signal green manufactured 
to existing formulas does not give a satis- 
factory signal colour when high intensity 
filaments are used. The Board of Trade 
and the Air Ministry Research Depart- 
ment are now working in conjunction to 
determine satisfactory formula?. There 
is no doubt, however, but that a question 
of this sort has already had the considera- 
tion of this Society. 

Certainly no effort will be spared in 
further research on the part of the Air 
Ministry to render these lights a sure 
safeguard for life and property during 
night flying. It may be that the Rules 
of the International Convention will 
require modification : we have only to 
realise that the average air speed of an 
aeroplane at the present day is about 
100 m.p.h.; thus in still air when two 
aircraft are meeting end-on the rate of 
approach is 200 m.p.h., or 33 miles per 
minute. It is quite obvious that the 
pilot has very little time to determine his 
action to avoid collision and, incidentally, 
a few aircraft have already reached the 
speed of 200 m.p.h. 

Consider the case of two aircraft 
meeting end-on at a rate of approach of 

33 miles per minute with their lights 
visible only at the ranges laid down, 
8 kilometres for the white head lights 
and 5 kilometres for the coloured side 

From the time of sighting the head 
lights to the moment of collision is only 
90 seconds and from the time of sighting 
the side lights to the moment of collision 
is only 50 seconds. The white light may 
be a stern light or the head light of a 
crossing machine ; it is not until the 
pilot is satisfied as to the rate of change 
of bearing of the white light or the 
character of the combination of lights 
presented to him that he can decide if 
lie is to alter course and in which direction. 
It looks as if the range of all navigating 
lights may have to be increased and side 
lights given the same range as the head 
and tail lights. 

Another form of light carried on board 
is that to facilitate landing, especially in 
emergency on an unilluminated area. 
Of these, the Holt wing tip flare consists 
of an inflammable aluminium composition 
suitably attached to the under side of the 
wing tip with means of ignition electrically 
from the pilot's cockpit. The pilot 
closes a switch when about 150 feet from 
the ground and illumines the ground 
through a radius of about 100 to 150 
yards, the flare giving about 6,000 candle- 
power. It lasts about two minutes, so 
again our pilot has not much time to 
think before depositing his ten thousand 
pounds machine (pounds sterling) and 
ten or a dozen valuable passengers in an 
unknown field on a dark night. The 
parachute flare is another means of 
lighting the ground for landing purposes : 
these flares are dropped through a tube 
on the side of the fuselage and fired 
electrically as they leave the tube ; they, 
of course, can be dropped from any height 
and give the pilot a chance of having a 
good look round before deciding to make 
a landing. At a height of about 1,000 
or 1,500 feet, they will light up roughly 
150 acres, being of about 40,000 candle- 

The usual Verey light is another means 
for use in emergency : it lasts about 
five or six seconds and will light up 
about five to six acres at a height of 
200 feet : this gives roughly 2,000 candle- 



During the War. r 1 1 * - English, French 
and German aii services were each 
independently developing means to a 
air pilots in night landing of aircraft on 
an nniUuminated area. 

In England. Two widely different 
oas were being developed simul- 
taneously, (a) the chemical flare, (b) the 
electric lamp. 

In France the development centred on 
elect rie lamps. In Gerraanv electric 
methods were also in favour. 

The German designs mainly embodied 
metal parabolic reflectors without [< 
and having filament lamps of medium 
power. The apparatus was evidently 
designed primarily to aid airships landing, 
and was devised for use either in t he hand 
or pivotally mounted on the machine 
structure. The beam angles were wide, 
indicating short range use. 

The French designs were more varied 

an<l covered the use .if electric wing tip 
lamps of small power, fuselage la 
and in one type four lamps in a row, i ach 
having its own lantern and parabolic 
reflector, the whole mounted under the 
fuselage, generally low down and between 
the landing wheels. Later, more power- 
ful filaments were adopted and provided 
with metal or silvered "lass reflectors 
and complicated front compound lens 
schemes. Both the French and German 
devices aimed at definite beams ol light 
of -onie more or less predetermined angle 
of divergency. 

The English devices as developed by 
the Air Force were much more varied in 
character and covered all the types 
experimented with both in France and 
Germany, but in 1918 the Research 
Department of the Air Ministry entered 
upon a new field and developed a very 
special type of gas-tilled iilament lamp 
of high power (1,000 to 2,000 candle- 
power) for use on the existing standard 
12 volt engine starting or general service 
accumulator. Naturally the use of such 
heavy currents as 50 to 60 amperes or 
more in a 12 volt filament lamp brought 
about many and .serious mechanical 
difficulties, the greatesi being an efficient 
method of " sealing in " the heavy 
current electrodes into the glass bulb. 

The early lanterns housing these high 
pow r er filament lamps were heavy and 
clumsy and mainly endeavoured to 

restrict the light into a predetermined 
beam. The present device with which 
the Research Department are experi- 
menting, comprises a high-power 12-volt 
filament lamp having filaments and 
sealing in devices of special design, 
mounted and held in such a manner in 
the lantern as to be capable of with- 
standing landing shocks without damage 
to the filaments or bulb. The lantern is 
streamlined and watertight and floes not 
restrict the light to a definite beam, but 
enables reflection and diffusion over 180°. 
Tie- weight of the complete landing lamp 
is 7 Hi. and does not involve the u£ 
a separate battery, hut functions from 
either the engine starting accumulator or 
the general service battery. Service tests 
have demonstrated its usefulness for 
ral ground illumination from a 
height of 500 feet and also for actual 
landings on an unilluminated locality. 

Pilots' opinions relative to the advan- 
tages of the chemical flares and the 
electric landing lamps vary considerably 
according to the individual bias of the 
pilot (some pilots prefer to land in the 
dark). The concensus of opinion at 
present shows : — 

(a) That for landing, the electric lamp 
is as good as the chemical flare. 

(b) For general illumination of the 
ground prior to landing at heights above 
500 feet, the chemical flare is superior 
to the electric lamp. At 300 feet the 
electric lamp showed up the ground quite 
clearly, and at 200 feet was superior to 
the chemical Hare ; with the latter the 
ground is clearer immediately below the 
machine, but with the electric lamp the 
ground is better illuminated in a fore and 
aft direction than laterally. (This was 
specially provided for in the design and 
is intentional to give greater range of 
visibility ahead.) 

(c) Once a chemical flare is switched 
on it must remain on. and may be a 
source of danger in misty weather, owing 
to the light being reflected back and 
dazzling the pilot. The ease of switching 
on and off the electric lamp is considered 
of inestimable advantage under all 

(i>) The limited number of chemical 
flares that can be carried compares 
unfavourably with the number of flashes 



and landings possible with the electric 
landing lamp. 

(e) The risk of fire in the event of a 
crash is, with the chemical flare, very 
great ; whereas with an electric lamp 
danger from fire is very small. 

Aerodrome Lighting. 

I now come to a very important 
function of light as an aid to aerial 
navigation, viz. : the lighting of aero- 
dromes to facilitate landing. I want to 
differentiate here between the lights 
employed for guiding a machine to its 
aerodrome and the lights designed to 
assist it to make a safe landing ; the 
former will be dealt with in a later part 
of the paper. 

Aerodrome lights for landing purposes 
may be divided into three classes : — 

(1) Obstruction lights. 

(2) Illumination of the actual ground. 

(3) Fixed illuminated signs to show the 
direction of the wind, etc. 

Obstruction lights are necessary to 
indicate to the airman the buildings, etc., 
round the aerodromes, over which the 
pilot must pass very close when gliding in. 

We have devoted our attention to 
perfecting the lighting of the London- 
Paris route : Croydon and Lympne are 
the aerodromes we have had to deal with. 
At both places obstruction lights are 
provided in the form of 60-watt in- 
candescent lamps placed at intervals 
along the ridges and highest points of 
the roofs, masts, etc. These lamps are 
run off the local town supply at Croydon 
and from the aerodrome power-house at 
Lympne. The incandescent lamp is en- 
closed in the usual watertight exterior 
fitting with the outer glass coloured red. 

Incidentally this display of red lights 
affords a very good means of recognising 
an aerodrome from the air. The lighting 
of the wireless masts has been rather 
special as they and the aerial slung 
between them form a nasty obstruction. 
We. have placed on top of each mast a, 
1000-watt J-watt type gas-filled lamp 
with a red outer glass cover and down 
each leg of the masts they are four- 
legged trellis masts — a series of 60-watt 
l-watt type white lamps of about 50 
candlepower, a third wireless telegraph 
mast has at the top a red lamp of the 

LOO-watt |-watt type. These again form 
a very good recognition mark for the 
aerodrome. A good deal of care and 
judgment must be exercised in the 
placing of obstruction lights. If, for 
instance, you place one at either end of a 
long building the pilot may well think 
that the space between is clear and do 
exactly what you are trying to avoid, the 
result being a bad crash into the building. 

Illumination of the Ground. 

Having kept our night mail aeroplane 
clear of the dangers of roofs, masts, 
chimneys, etc., in the same way as you 
place light buoys on the shoals of a 
channel, we come to the most important 
part, viz., getting safely on to terra jirnia. 
What we want to do is to flood the whole 
ground with light without causing any 
confusing shadows or bringing any glare 
into the pilot's eyes at the moment he is 
exercising the greatest nicety of judgment 
in bringing five tons to earth without 
bumping it. The last portion of the glide 
of a heavy machine may be some 200 
yards at a height of not more than 10 or 
15 feet from the ground. If, then, we 
were to put a circle of very intense 
candlepower lamps round our aerodrome, 
in the same manner as the large open-air 
skating rinks in Switzerland are illumin- 
ated, although the whole area would be 
better lit up than Piccadilly Circus, we 
should be bound to have some lamps 
shining in the eyes of the pilot, and there 
would be a multitude of shadows to con- 
fuse him. It is obvious that at whatever 
height you put the lamps he is bound to 
be dazzled at some portion of his glide. 
I might add that such a system would 
be enormously expensive. Various 
systems have been tried, starting from 
the Money flare system. The Money 
flare consists of asbestos composition 
compressed in a wire cane of about 10 in. 
diameter : the whole is soaked in paraffin 
and placed in a metal bucket. When lit 
it lasts about three hours, and throws a 
fairly good illumination over a circle of 
about 20 yards radius. The method of 
employing these .Money flares is to lay 
out a number in the form of an " L," 
the long arm being in the direction of the 
wind and the short arm at the windward 
end. This system serves not only to 
indicate to the pilot the direction in 



which he must land, hut is sufficient to 
indicate the exact level of the ground 
without in any way dazzling the pilot. 
It is a well-tried product of the War, and 
most night-flying pilots prefer it to any 

The system is, however, costly in 
labour; it takes a party of half a dozen 
men to lay out the Hate-, and with any 
shift of wind they must be all rearranged 
in the shortest possible time. A sub- 
stitute for the Money flare landing '" L " 
for Service purposes has been tried where 
electric current is available, by placing 
ordinary incandescent lamps at intervals 
along a cable and running this out in the 
necessary position. It also requires a 
number of men to handle this and shift 
it quickly. 

This last system has been elaborated on 
at Croydon aerodrome, where naturally 
the overhead charges for labour are cut 
down to a minimum. 

The provisions of the International Air 
Convention had to be met by the installa- 
tion of the " double L " system, in which 
the landing area of an aerodrome is 
marked out in three zones, necessitating 
the employment of two " L's " back to 
back, used on the principle already 
described, except that one " L " is for 
machines "taking off," the other for 
those landing. 

Landing " L's." 

To obtain this effect, 24 electric lights 
are sunk into the ground in cast-iron 
watertight boxes, so placed as to allow 
of two " L's " being indicated for each of 
eight different wind directions. The 
lights are connected up through various 
junction boxes to a control switch in an 
office on the edge of the aerodrome ; the 
switch has a rotating handle enabling one 
operator to indicate any given wind 
direction by turning the handle, thus 
dis | tensing with the labour required when 
flares are used. The electrical portion 
of this system did not present much 
difficulty, but certain problems in illumin- 
ation caused a considerable delay. As 
originally designed, the ground lamps 
were covered by flat plate glass discs, with 
a white enamelled reflector of the intensive 
pattern behind them ; this naturally 
resulted in the light being distributed 
through a comparatively narrow arc, so 

that though the lights were easily seen 
from a few thousand feet when nearly 
over them, they were invisible from a low 
angle — when they are most required. 
Experiments were proceeded with, and a 
new type of slightly dome-shaped glass 
cover, aided by an extensive reflector 
behind each lamp, appears to disperse the 
light suitably. Owing to practical diffi- 
culties in the making of these glass covers, 
conclusive tests of the new system have 
not yet been made. 

The system described by no means 
fill the ideal of so lighting the ground as 
to make it as easy to land on by night 
as by day. 


The use of powerful searchlights is the 
first thing to strike one. One objection 
to these is their running cost, the 36-inch 
searchlights at Croydon taking I 10 
amperes at 60 volts across the arc, which 
means the consumption of about 51 units 
of electricity per night per projector, an 
amount which would cost the ordinary 
householder about 30s. per night. 

One method of using a searchlight tor 
landing is to place your projector on the 
leeward side of the aerodrome and the 
pilot glides in over it. It serves as a wind 
indicator and to illuminate the ground. 

The shadow trouble confronts us at 
once ; if the pilot lands in the beam his 
own shadow is projected ahead of him. 
For this reason the method is not only 
unpopular but unsafe. If we concentrate 
the beam, a very narrow path is illumin- 
ated but the pilot can now come in 
nearly over the projector and make his 
landing immediately alongside the beam. 
This is fairly satisfactory, but here again 
we are troubled by the objectionable 
habit the wind has of shifting, which 
means we must shift our projector ; to 
shift a projector round a wet aerodrome 
is no easy matter unless we provide a 
motor lorry or instal a permanent set of 
rails and a trolley. 

We have considered, however, the value 
of the intense illumination given by a 
large searchlight sufficient to instal at 
Croydon three 36-inch projectors which 
can be used for illuminating the ground 
and also for other purposes. 

These three projectors are placed 
roughly at the angles of an equilateral 



triangle and means are provided for 
switching any one of these on. One 
angle of the triangle is always approxi- 
mately to leeward, the worst case being 
when the wind is blowing at right angles 
to one side of the triangle, when the 
aeroplane will be 60° off the wind if the 
pilot follows the direction of the beam. 
To compensate this we have our illumin- 
ated landing " L," which gives him the 
true direction. This method of landing 
down beam is not so satisfactory as 
landing across the beam. In this case, 
a beam having a divergence of 45° is 
used to produce a very efficient floodlight ; 
we switch on that beam which is most 
approximately at right angles to the 
wind ; the land " L's " together with the 
beam give the pilot his direction. 

It is thought that this will be the most 
satisfactory method of illuminating the 
ground for landing purposes. 

The French have already adopted a 
somewhat similar method to the last. 
They have equipped a motor lorry with 
four floodlights of a type produced by 
Barbier-Benard et Turenne, a sample of 
which is on the table. The source of light 
in these is a 1500-watt J-watt type gas- 
filled incandescent lamp placed at the 
focus of a split 200 mm. dioptric lens. The 
light emitted equals approximately 
15,000 candles, and illuminates an arc of 
180° in the horizontal plane so that 
roughly they get 60,000 to 75,000 candles 
from their lorry as against something of 
the order of a million candles from our one 

The French method is to direct their 
floodlights, a line of four on poles along 
the roof of the lorry, and at a height of 
about five metres from ground level, so 
that the axis of the beam is at right angles 
to the direction of the wind ; a tail of 
two or three incandescent lamps on a 
cable laid out either end of the lorry in 
continuation of its length indicates the 
direction of the wind. There is a second 
lorry carrying an engine and generator 
to provide the. necessary current. The 
whole apparatus is consequently mobile 
and can be moved to any point of the 
aerodrome according to the direction of 
the wind. At Le Bourget Aerodrome, 
Paris, it is proposed to have connections 
at various points of the aerodrome to 
the local supply so that it will only lie 

necessary to more the lamp lorry to any 
one of these tapping points and connect 
on. I have lvot gout' into the compara- 
tive cost of the French and our own 
method. They have been making use 
of apparatus obtainable by them at very 
small cost from their surplus war stores 
and we have been doing the same. 

You must remember that the petrol 
and oil alone costs about 44s. an hour 
to keep a two-seater machine in the air. 
Other incidental expenses of experimental 
work at night are heavy. There has been 
no regular commercial night flying to 
give us the practical experience we want ; 
we hope to see some in the near future, 
and passengers may rest assured that 
night landing on the British aerodromes 
of the London-Paris route will be quite 
a safe operation on any ordinary night. 
I say any ordinary night, but there is 
always the difficulty of fog and mist. 
This brings me to the very important 
subject of fog- piercing lights. As is well 
known to all illuminating engineers, this 
problem has had the closest study for a 
great many years from the point of view 
of street lighting, marine lighthouses, 
railway signalling, coast defence search- 
lights, etc. I was occupied myself on the 
last problem some twelve or thirteen 
years ago when we were trying to arrive 
at a satisfactory gilded reflector. The 
problem is not yet solved and is still 
occupying the attention of the authorities. 
Nor have the problems of lighting a street 
on a foggy day, the marine fog- piercing 
lights or the railway signal been satis- 
factorily solved. Meanwhile flying has 
arrived and the solution of the problem 
has become almost a vital necessity for 
commercial flying in our unpleasant 
climate. The. Research Department of the 
Air Ministry has directed a great deal of 
energy and study towards the problem 
since the war and I believe we are on the 
eve of finding a satisfactory solution at 
any rate for an ordinary comparatively 
thick ground mist, but we must own 
to still being defeated by the good old 
London peasoup fog. 

As is well known, coloured lights have 
under certain conditions a greater pene- 
tration in fog and mist, and experiments 
have been made at various times with a 
view to developing some form of coloured 
mist - piercing light or flare. Two 



systems show greater promise than any of 
the number tested ; one consists of an 
ordinary dissolved acetylene pressure-fed 
flame into which is introduced mechani- 
cally a liquid strontium composition; this 
produces a reddish flickering flame of 
considerable intensity. 

The second system is the result of 
pyrotechnical research, and is intended 
for emergency use only, in cases where a 
machine is obliged to descend at .1 par- 
ticular aerodrome in a comparatively 
dense mist. 

Large composition flares are employed, 
which are ignited electrically, and burn 
for about five minutes with a very in1 
flame having a light value of about half a 
million candlepower. Theseflares bavenot 
yet been actually used by a machine land- 
ing, experimental flying in thick weather 
not beinga popular hobby. They are com- 
posed principally of magnesium, vai 
other earth salts being introduced to give 
the necessary tnist-penetrating colours. 

Illuminated Ground Signs. 

I must pass on to what has been done 
in the way of illuminated ground signs. I 
have already described the landing " L's" 
which have been installed at Croydon. 
The only other illuminated ground sign 
we are making use of is one devised for 
emergency landing grounds. 

These places are merely open fields 
with a fairly level surface, offering no 
facilities beyond the tact that a machine 
can land on them. No personnel are 
available, and in most cases the use of 
electricity for lighting purposes is out of 
the question: at the same time these 
grounds, to he of any value to eight 
flying, must indicate to a pilot, first their 
position, and, secondly, the direction 
of the wind. It will easily be seen that 
with neither labour nor light available, 
except at a prohibitive cost, the efficient 
lighting of these grounds presented 
considerable difficulty, particularly as the 
most stringent economy was essential. 

However, this problem is now solved, 
after a few failures and disappointments ; 
a combined recognition light and wind 
indicator has been evolved which meets 
the demands of both efficiency and 
economy. This consists of an illuminated 
"T" sign, 011 the same principle as the 
day landing " T's " used during the War. 

The long arm of the " T " is U« » feet, the 
- pieces at the top being 1" feet over 
all : each arm is illuminated by li 
placed round a light source at the junction 
of the arms, a light of 27.<h>o candlepower 
being thrown along each arm. The 
result is that the " T '" is visible as a 
flashing light at about 1m miles from any 
normal flying height, thus enabling a 
pilot to locate an emergency landing 
ground at any reasonable distance. 

The shape of the " T " is char and 
distinct at about three miles, and as it is 
free to rotate with changes of wind- 
direction it also acts as a landing light : 
in addition, the velocity of the wind is 
indicated by different coloured lamps. 

The whole apparatus is automatic in 
• li. being lighted at dusk and extin- 
guished at daylight, am! is equipped for 
six months unattended operation on the 
A.G.A. principle, thus solving what was 
tic most difficult problem in the provision 
of an economical ground lighting system 
on aerial rouf 

The illuminant used is dissolved acety- 
lene gas stored in portable steel cylinders 
which are connected to a light-producing 
apparatus of the Dalen type, in which air 
and automatically mixed in the 

right proportions to ensure perfect com- 
bustion. The incandescent mantles used 
are of special manufacture giving an 
intense white light, and a mechanical 
arrangement is provided which causes 
the automatic replacement of defective 
mantles by new on 

The fight is controlled by a sun valve 
worked by the action of solar radiation, 
anil which is so designed as to be in- 
operative under any temperature cha 1 
Briefly, the system employed is that a 
central black body is surrounded by 
highly polished pillars ; light, and there- 
fore heat, falling upon these elements is 
absorbed by the black centre and reflected 
by the outer gilt columns. Consequently. 
the black portion expands under a given 
influence to a greater extent than the 
polished elements ; this difference in 
expansion is utilised to open and close a 
gas valve, turning the light off and on 
according to tin' prevailing degree of light 
and darkness. 

It is of interest to note that a valve of 
this type brought the Croydon light into 
action during the last eclipse of the sun. 



Aerial Lighthouses. 

I have described to you the various 
forms of lights used at an aerodrome, 
but we have still to consider the lights 
employed for helping the pilot to navi- 
gate his aircraft along the aerial highway 
and when nearing his destination to 
guide him into port. These may be 
covered by the general term Aerial 
Lighthouse and be classified as (a) 
Navigating Lights, and (b) Local Pilotage 

Navigating Lights. 

The earlier forms of aerial lighthouse 
were the small portable lighthouses used 
in France at various aerodromes in order 
to help our pilots during night flying 
operations ; these lights were of the 500 
mm. half-optic type with open type 
burners consuming dissolved acetylene 
gas and served their purpose satisfac- 
torily. But for the navigation of 
commercial aircraft we have had to 
consider the provision of aerial lighthouses 
in the same way as the marine lighthouse 
is provided for mercantile shipping. 
The solution of this problem was very 
materially assisted by a careful study of 
the latest developments in marine light- 
house engineering, the two subjects — 
marine lighting and aerial lighting — are 
very similar in their basic principles. 
The same light source can be used and 
the same methods of distributing it can 
be employed, with one important addition. 

This is that whereas in marine light- 
house work the designer has only to aim 
at directing light-rays to sea level through 
a narrow vertical arc, and is wasting any 
light otherwise dispersed, the aerial 
lighthouse must throw its rays through 
practically the whole upper hemisphere. 

To explain this more fully, let us 
consider a large marine light, or " making 
light," situated on the coast. The 
lenticular apparatus of such a light is 
designed to project the greatest available 
light power to the horizon, so that the 
maximum intensity is received by an 
observer in a ship when he is at the 
geographical range of the light- that is, 
at the extreme useful range. The 
scattering of any light more than a few 
minutes of a degree above the horizon is 
theoretically undesirable from a strictly 
efficient standpoint, as this scattered 

light cannot possibly reach the eye of an 
observer near sea level. 

However, in practice, the light beam 
emanating from a lens face is invariably 
strongly divergent, owing to the size of the 
light source employed ; this vertical 
divergence is usually about 8 or 10 

Of this light dispersed vertically, that 
below the optical axes of the lenses 
renders the light visible at all points 
between it and the horizon, and is there- 
fore essential ; on the other hand, nearly 
all the light thrown above the optical 
axes is useless to the mariner, but can be 
utilised by the aviator. 

For example, an observer approaching 
a " making " light at an altitude of, say, 
6,000 feet will obviously be able to see 
the light at a much greater range than 
would be possible from sea level, but 
continuing his flight towards the light, he 
will pass over the main beam while still 
at a considerable distance, owing to the 
fact that the base subtended by the beam 
decreases very rapidly as the light is 

This will be realised if we consider for 
a moment the case of a marine light 
having a light beam with a total vertical 
divergence of 10 degrees — five degrees 
below and five above the horizon ; 
aeronautically, we may assume that the 
beam of light has a vertical divergence of 
five degrees only, as the light below the 
optical axis is useless to the aviator. 
Given that the light power at the centre 
of the beam is one hundred thousand 
candlepower, the maximum range of the 
light, under the atmospheric conditions 
normally obtaining in the North Atlantic- 
Ocean will be about 44 miles. At this 
extreme range, the base subtended by the 
beam is about 20,000 feet, so that our 
observer flying at 6,000 feet will be well 
within this beam ; at 20 miles the base 
decreases to a little more than 9,000 feet, 
while at 15 miles it is 6,900 feet. At this 
distance the observer will be very near 
the edge of the beam, with the result that 
he would in all probability lose the light. 
owing to the small light value reaching 
him; retaining his height— 6,000 feet — 
he will pass out of the beam entirely when 
1 1 miles from the light. 

It is obviously impracticable for 
aviators to reduce height steadily when 



approaching a lighthouse in order that 
they may remain within the beam, 
bo it was therefore necessary to investi- 
gate ways and means of distributing 
sufficient light power into the upper 
hemisphere to enable aircraft to use 
aerial lights when flying at any reason- 
able altitude. 

The problem has demanded much 
more t bought and experiment than would 
a1 firsl appear; not only has it been 
necessary to obtain complete statistics 
of atmospheric absorption at varying 
degrees <>f elevation, but the personal 
equation also called tor considerable 

It will be readily appreciated thai there 
is a great difference Between picking up 
.1 light from the bridge of a Blow-moving 
vessel and picking up the same light 
from an aeroplane moving at anything 
up in 200 miles per hour. In the first 
case, the marine observer is usually very 
fit and with his nervous system in a calm 
state; he has binoculars to assist his 
eyes, is in no hurry, and probably has 
very little to think about beyond the 
light he is looking for, and the hot 
coffee he drinks at intervals to keep him 
alert . 

The other side of the picture is a tired 

and worried pilot in a cramped position, 
his nerves on edge through thinking 
of a dozen different things simultaneously, 

every sense strained to catch some real 
or fancied difference in the behaviour of 

his engines, his eyes wearied by staring 
ahead into a wind of terrific velocity, and 
to whom every second of time is highly 
important. It was imperative to allow 
for conditions such as these in the design 
of aerial lighthouses. 

Experience proved not only the 
absolute necessity of complete homo- 
geneity of light throughout the 180° to be 
illuminated, but also that the light values 
obtained must not vary to any appreciable 
extent as a light is approached. It is 
essential that the light intensity available 
to an observer's eye shall remain nearly 
constant from the moment that the light 
is " picked up" until he is passing 
over it. 

Various methods of obtaining this dis- 
tribution of light were tried out in the 
most practical way by using aeroplanes 
and airships carrying experienced 

observers who spent many cold but 
interesting nights in the air. The 
information gained was of the greatest 
value and used in conjunction with tie- 
results of research work carried out by 
mathematical experts has made possible 
the designing of a lighthouse which will 
meet the demands of the aviator. 

The practical trials of some of the 
earlier forms of optical apparatus 
demonstrated the fact that dark spots 
which were not suspected existed «t 
certain angles of elevation. These 
results were subsequently confirmed by 
careful mathematical calculation and 
these calculations verified by a prominent 
Oxford mathematician : the actual curve 
of light values obtained is shown in 
diagram "' A." 

Diagrams '" B " and " C " BJhow the 
intensity al varying elevations of later 
forms of optical apparatus which we 
have had under consideration, Diagram 
•' I) (p. 56) being ■> range curve. 

Efficiency, reliability and economy 
were the desiderata aimed at in lighting 
the aerial routes ; having reached an 
efficient method of distributing light it 
was then necessary to consider the other 
two factors conjointly. Reliability could 
have been obtained by setting up an 
expensive system of attended lights bul 
economical considerations forbade this, 
and as yet there are no " light dues' 
paid for aerial lighthouses. 

After consideration of many types we 
came to the conclusion that an automatic 
acetylene gas-operated type of light- 
house of the third older was the most 
suitable, the reliability and economy of 
this apparatus having been satisfactorily 

A lighthouse of this type, supplied by 
the (bis Accumulator Company, of Brent- 
ford, has been in operation first at 
Hounslow later at Croydon Aerodrome, 
since December 1919 ; this light will 
shortly be moved to a more useful 
position at Tatsfield Hill, Surrey, after 
certain alterations have been made to 
the optical apparatus resultant on the 
experiments of the last two years. (See 
Fig. 2, p. 54.) 

A second light of the same type will be 
established at Hartley, near Cranbrook, 
in Kent. Both these lights will be 
visible at ranges of over 35 miles, and will 















_l z 







L_ LJ 



























s a 

10 . ■+ w o 



be equipped for twelve months' un- 
attended operation. 

They are of the revolving type, the 
rotation of the lens being obtained by the 
movement of certain sensitive diaphragms 
which are operated by the gas passing 
under pressure to the burner ; on the 
light being extinguished by a sun valve 
the optic ceases to rotate. This sun 
valve together with the automatic 
mantle replacement gear also employed 
has already been described in my remarks 
on the automatic wind-indicator for 
emergency landing grounds. 

The experience gained baa so Ear been 
only in our English climate. We hope 
this .summer to Lave a similar aerial 
lighthouse in operation in Egypt, which 
will give us further data to work on for 
the essential lighting of the aerial highway 
to the East. 

Fit.. 2. First Aerial Lighthouse at rlounslow. 

Local Pilotage Lights. 

In addition to the Long range navigating 
lights placed at selected points on the 
route giving the greatest all-round 
visibility it was necessary to consider the 
best form of local pilotage light. It 
was found that an ordinary flashing light 
with a character that was absolutely 
distinct and unmistakable to a trained 
observer was not always easily picked 
up by the average pilot when viewed 
from over the lights of a town. This 
was due to a certain extent to the con- 
fusion caused by the surrounding lights, 
as well as to the difficulty a night pilot 
has in concentrating on anything but his 
machine. It was found that a light of 
distinctive shape was much more easily 
picked up when surrounded by other 
lights, and the local pilotage fights at 

Croydon and Lympne Aerodromes, also 
made by the Gas Accumulator Company, 
are the result of the experiments in light 
shapes ; each of these lights consists of two 
distinct units ; the upper unit is composed 
of one 1500-watt ', watt type gas-filled 

Pro. 3.— Pilotage Laghl by Day. 

lamp placed within a 500 millimetre 
drum lens, and with a 36-inch parabolic 
reflector below it. This unit is super- 
imposed on a truncated cone, 21 feel in 
diameter at the base, 3 feet diameter at 
the top, and l-j feel high. This cone is 
illuminated by four lamps similar to that 
in the top unit, placed equidistantly 
around the periphery of the apex of the 
cone and projecting about two feet. 
The cone is painted with a special light- 
reflecting composition, and is visible 
as a triangular patch of light at a 
distance of 15 miles. The upper unit has 
a nominal ranee of 25 miles, the observer 
being at an average flying height. 

The two units can be synchronised to 
give any required character, and it has 
been found that the shape of the light 

4.— Pilotage Light at Night. 

renders it remarkably distinct even when 
surrounded by other Hashing lights, thus 
sol vine a difficult problem, that of pro- 
viding observers untrained in navigation 
with a light that is easily distinguishable, 
when placed in a thickly populated 


90 85 8o° 75 70 65 6o° 


30 40 

Candlepower In Hundreds. 

DIAGRAM C. — Liiiht Values for Later Aerial Lighthouse!, 

Fkj. 5. — Pilotage Light by Day, with Aeroplanes in the Background. 

C 2 



district. Diagram " E " shows the range 
curve for the upper unit of this light 
minus the parabolic reflector. 

Incidentally, it may be remarked that 
during the War a small lighthouse of the 
500 mm. split-drum lens type, with open 
burners, was seen at a range of over 30 
miles from an altitude of six thousand 
feet. This light was placed in a lonely 
tract of country, no other lights being 

ranges ; it will be seen that under 
favourable conditions a pilot w T ill always 
be within the range of two of these lights 
while flying along this route. 

Marine Liqhthoi 

The question of modifying marine 
lighthouses to inert the ueed of aviators 
has also received consideration, the 

Ron,. .. M.I. 

A. for Lijrit l.l.»..l, i til 
■miHia riaikli 

B-for L.jM latWMltjl M,n. 


Diagram D. — Range Curve for Later Aerial Lighthouse. 

exhibited within a radius of many miles. 
Experiments with similar lights under 
peace-time conditions of town illumina- 
tion have, shown that such lights are 
useless to aviators, again demonstrating 


Diagram E. — Illustrating relation between 
height and range. 

that war-time experience in aeronautical 
lighting was of no value when applied to 
peace conditions. 

A map (exhibited at the lecture) shows 
the positions of the navigating lights on 
the London-Lympne air route, with their 

advice and assistance of the Corporation 
of Trinity House having been of the 
greatest value in this matter as well as 
on the whole question of aerial light- 

A number of observations have been 
made from the air, and it has been found 
that certain existing marine lighthouses 
are of considerable assistance to the aerial 
navigator under certain conditions. For 
instance, the Nore Light Vessel has been 
observed at a distance of 30 miles, 
the observer being at about 1,000 feet : 
from the same height, Orfordness Light 
has been seen at 27 miles and the red 
flashing light on the Gunfleet Shoal 
at 34 miles. A green light, the Mouse 
Lightship, has been picked up at 28 miles 
from a height of about 1,500 feet, while 
the bearing of a really high-powered light, 
Cape Gris Nez, has been obtained at 68 

In view of these results of practical 
observation it is not at present proposed 
to make any alterations to marine 
lighthouses in this country, though it is 
recognised that a large number of these 



lights are useless to aviators, being- 
obscured in certain directions either by- 
design, or by trees, buildings, etc. 

Signalling and Landing Lights. 

The " Rules as to Lights " framed at 
the Convention relating to International 
Aerial Navigation* have already been 
mentioned. Some particulars of the 
recommendations in regard to signals and 
lights used to facilitate night landings 
at aerodromes may also be of interest. 


In Section II. the following rules as to 
signals are laid down : — ■ 

An aircraft wishing to land at night on 
aerodromes having a ground control 
shall before landing : — 

Fire a green Verey's light or flash a green 
lamp, and in addition shall make by 
international Morse code the letter- 
group forming its call-sign. 

Permission to land will be given by the 
repetition of the same call-sign from the 
ground, followed by : — 

A green Verey's light or flashing a green 

The firing of a red Verey's light or the 
display of a red flare from the ground 
shall be taken as an instruction that 
aircraft are not to land. 

An aircraft compelled to land at night 
shall, before landing, fire a red Verey's 
light or make a series of short flashes with 
the navigation lights. 

When an aircraft is in distress and 
requires assistance the following shall be 
the signals to be used or displayed, either 
together or separately : — 

(a) The international signal S.O.S. by 
means of visual or wireless signals. 

(b) The international code flag of 
distress, indicated by NC. 

(c) The distant signal, consisting of a 
square flag having either above or below 
it a ball, or anything resembling a ball. 

(d) A continuous sounding of any 
sound apparatus. 

(e) A signal consisting of a succession 
of white Verey's lights fired at short 

* Air Convention, White Paper, No./6"0, 1920, 

To warn an aircraft that it is in the 
vicinity of a prohibited zone and should 
change its course, the following signals 
should be used : — 

(a) By day : three discharges, at 
intervals of 10 seconds, of a projectile 
showing, on bursting, white smoke, the 
location of the burst indicating the 
direction the aircraft should follow. 

(b) By night : three discharges, at 
intervals of 10 seconds, of a projectile 
showing, on bursting, white stars, the 
location of the burst indicating the 
direction the aircraft should follow. 

To require an aircraft to land, the 
following signals shall be used : — 

(a) By day : three discharges, at inter- 
vals of 10 seconds, of a projectile show- 
ing, on bursting, black or yellow smoke. 

(b) By night : three discharges, at 
intervals of 10 seconds, of a projectile 
showing, on bursting, red stars or lights. 

In addition, when necessary to prevent 
t lie landing of aircraft other than the one 
ordered, a searchlight, which shall be 
flashed intermittently, shall be directed 
towards the aircraft whose landing is 

In the event of fog or mist rendering 
aerodromes invisible, their presence may 
be indicated by a balloon acting as an 
aerial buoy and/or other approved 

In fog, mist, falling snow or heavy 
rainstorm, whether by day or night, an 
aircraft on the water shall make the 
following sound signals with a sound 
apparatus : — ■ 

(1) If not anchored or moored, a sound 
at intervals of not more than two minutes, 
consisting of two blasts of about five 
seconds duration, with an interval of 
about one second between them. 

(2) If at anchor or moored, the rapid 
ringing of an efficient bell or gong for 
about five seconds at intervals of not more 
than one minute. 

Night Landings on Aerodromes. 
The signals shall be as follows : — 

(a) A red light shall indicate a left- 
hand circuit, and a green light shall indi- 
cate a right-hand circuit. The right-hand 



zone will be marked by white lights 
placed in tin- position of an " L," and the 
left-hand zone will be similarly marked. 
The " L's " shall be back to back, that is, 
the long sides of the " L's " will indicate 
the borders of the neutral zone, the direc- 
tion of landing shall invariably be along 
the long arm of the " L," and towards 
the short arm. The lights of the " L's " 
should be so placed that the lights indi- 

cating the top extremity of the long arm 
shall be the nearest point on the aero- 
drome upon which an aeroplane can safely 
touch ground. The lights indicating the 
short arm of the ' ; L " should indicate 
the limit of safe landing ground for the 
aeroplane, that is, that the aeroplane 
should not overrun the short arm. 

(A system facilitating the saving of 
lights and personnel is described.) 


Thk Chairman (Major-General Sir 
Frederick Sykes) said that the subject on 
which Colonel Blandy had addressed 
them that evening was one of the most 
important with which those responsible 
for the development of commercial avia- 
tion had to deal. The two main problems 
that required solution before commercial 
aircraft could, without financial assistance 
from the State, enter into free and 
successful competition with the older 
means of transport, were the development 
of a cheap economic engine and flying by 
night and in foggy weather. 

It was obvious that the value of the 

superior sj d of heavier-than-air craft 

over rail and steamship was halved if the 
aeroplane had to lie idle during the hours 
of darkness. This was, of course, par- 
ticularly unfortunate where short dis- 
tances and good rail communications, as 
between London and Paris, were con- 

On longer routes, such as he would like 
to see established between Cairo and 
Karachi, the aeroplane's superior speed 
was most clearly demonstrated ; and even 
flying by day only it could reduce the 
journey on this route from nine to four 
days. But if night flying were possible 
and the route properly illuminated, the 
distance could easily be covered within 
48 hours. 

Flying, and more particularly landing 
and getting oft* from an aerodrome in thick 
weather, was a more difficult problem 
than night flying, and by reason of the 
peculiarities of our climate, particularly 
important for us. 

The great asset of flying was speed. 
But speed was of little commercial use 
without regularity, and fog was at present 

a great difficulty in the way of regular 
air services. The discovery of some 
method of illumination to penetrate fog 
would be of the greatest possible assistance 
to flying from this point of view. 

There were two ways of facilitating 
night flying ; one was by wireless direc- 
tion finding (with which they were not 
concerned that night). The other was 
by an efficient system of illumination, 
implying illumination of the machine, 
the route and the aerodromes, and the 
development of a sure, simple and quick 
system of signals from and to aircraft. 
As Colonel Blandy had mentioned, they 
had made considerable progress since the 
war, and arrangements were now in 
course of completion whereby the English 
section of the London-Continental air 
route, Croydon-Lympne, could at short 
notice be opened for night-flying. In 
this connection he was glad to see Sir 
Acton Blake present, for it gave him (the 
Chairman) the opportunity of thanking 
him, not only for the very keen interest 
that Trinity House had taken in night- 
flying, but for the very material assistance 
which they had rendered, especially in 
the design of aerial lighthouses. They 
had even offered to make alterations in 
their marine lighthouses so as to be of 
greater assistance to pilots of aircraft. 
Many of these lights, as Colonel Blandy 
had said, were already visible from the 
air, and in these days of economy the ex- 
pense involved was too great to warrant 
the alteration ; but the suggestion had 
given confidence that where so much more 
than an inch had been already offered, 
they might, when need arose, come 
forward in the future and without fear of 
a rebuff, ask for an ell. 



Meanwhile, they required all hands on 
deck to master the problem. Colonel 
Blandy had already done, and was doing, 
a great deal for communications as affect- 
ing aviation. But they also wanted out- 
side support and assistance, and in this 
question of night and fog flying and the 
illumination of aerodromes and air routes, 
the experience of the Illuminating En- 
gineering Society could help to solve 
many of the problems confronting them. 
He therefore asked the Society to give 
them the benefit of its extensive know- 
ledge, experience and co-operation. 

Colonel Mervyn O'Gorman, on behalf 
of the Royal Aeronautical Society, ex- 
pressed his pleasure at being present at 
this joint meeting. The subject was 
one of clear common interest to both 

The paper contained much interesting 
information, and showed that there was 
much yet to be learned in this new field. 
One point, in connection with lighting 
arrangements on aircraft, to which he 
attached considerable importance, was 
the limitation of the risks of fire. The 
risk of fire in the event of an aircraft 
" crashing " was to be borne in mind in 
the lighting arrangements, and though 
fires did not happen very often, the conse- 
quences might be serious when they did 
occur. If one ascribed one-half of such 
conflagrations to the hot exhaust pipe 
setting fire to oil or wood and thence to 
leaking petrol, the other half was pro- 
bably due to electric causes, such as 
severed wires or sparks from the magneto 

It would be of service to aerial naviga- 
tion if electrical engineers would evolve 
some method of wiring which would refer 
the spark that occurs on breaking any 
circuit to some safe place. 

He would like to ask why red and green 
were so frequently used to distinguish 
signals, in view of the fact that a fair pro- 
portion of people of the male population 
were more or less colour-blind. The re- 
jection of persons with such abnormal 
vision involved a limitation in the choice, 
whether of pilots, or signal men, or engine 
drivers. Could not a flicker be substituted 
for the colour distraction \ 

Finally, Colonel O'Gorman referred to 
the importance of careful design in rela- 

tion to weights in navigating lights. 
Every pound of weight carried in equip- 
ment had to be deducted permanently 
from the very restricted margin of paying 

Major-General Sir Sefton Brancker, 
K.C.B., expressed his interest in the paper. 
There was one point on which he was not 
quite in agreement with the lecturer, 
namely, the question of strongly illu- 
minating the surface of the aerodrome 

He thought that powerful directing 
lighthouses were necessary to guide the 
aircraft to the aerodrome, but that having 
arrived over it, very little lighting was 
necessary for the actual landing. During 
the war a line of small electric bulbs had 
been found quite sufficient. He thought 
it would be unwise to spend any money 
on illuminating the surface of an aero- 
drome until it had been proved that the 
other method was unsound. He realised 
that the use of the T system of lights for 
indicating the direction of wind had been 
approved as the international method, 
but he personally thought its installation 
was somewhat complicated and expensive, 
and that a system which showed a V with 
only three lights was quite sufficient and 
much simpler. 

The lecturer had rather laid stress on 
the great difficulties of night flying. 
Personally he did not think that these 
difficulties were as great as they were 
made out. Unfortunately, since the end 
of the war, very little night flying had 
been carried out, but we must remember 
that, during the war, pilots were up over 
London on many nights with very inade- 
quate lights to help them, and that in 
France night bombing raids were carried 
out night after night in all sorts of weather 
and under conditions which practically 
eliminated all lights, except at the aero- 
drome just prior to landing. 

Crashes during these operations were 
remarkably few. He thought that night 
flying on commercial routes would be 
much easier and come quicker than was 
expected. Its success depended on 
ground organisation, of which the two 
most important items were powerful 
lighthouses along the routes and a very 
thorough and reliable system of wireless 



Sir Acton Blake (Deputy Master of 
Trinity House), said that, as a seaman, 
he recognised tliat there were many con- 
ditions in the use of light for aviation 
which were generally similar to those 
met with at sea. He noticed that 
Colonel O'Gorman had disapproved of the 
conventional use of red and green lights 
on the ground that a considerable pro- 
portion of people were colour-blind. 
This, however, was not in accord with his 
own experience. 

Trinity House had a very large number 
of people under its control, and although 
cases of colour-blindness occurred they 
were very occasional. Red and green 
lights had proved useful to seamen, and 
he thought tjiey would likewise lie service- 
able in flying by night. 

He had listened to Colonel Blandy's 
paper with great interest, and he could 
not but be struck by the great distance u e 
had travelled since the days of ballooning, 
when they had no lighting appliances to 
aid them. 

In his experience attempts made at 
colouration with a view to securing good 
fog-penetrating power had not been a 
success. As illustrating the degree of 
visibility attained in marine lighting, he 
might mention that the tight at the 
Lizard was Frequently seen at a distance 
of 100 miles. 

The lecture contained much food for 
thought, and the Society was to lie con- 
gratulated in bringing this important 
subject forward for discussion. 

Mr. Haydn T. Harrison said that the 
paper was of historic value. Tt was. he 
believed, the first occasion on which a 
paper had been read on this important 
subject, and it dealt with many points 
that might have a vital bearing on night 
flying in the future. 

Mr. Harrison said that he had had to 
deal with similar problems in connection 
with searchlights for the Navy, but in 
their case the chief consideration was the 
intensity of illumination necessary to 
render a specified distant object visible, 
and the quality of light most favourable 
to high visibility and good penetrating 
power. He personally believed that, 
with a given intensity, one could localise a 
red or yellow light from a greater distance 
than a light giving the violet end of the 

spectrum, but this was not the same pro- 
position as making a distant object 
visible to an observer near the light 
source, in which case the question of 
colour of light did not affect the result 
as much as intensity. The use of a 
screen naturally caused loss of light in 
proportion to the original spectrum. It 
had been said in the past, and was still 
commonly asserted, that one could Bee 
an oil light in a lighthouse better than an 
arc light ; bearing in mind the comparative 
intensity of light this appeared absurd : 
nevertheless a distinction must be drawn 
between the visibility of a distant illumin- 
ated object ami the observation of a dis- 
tant luminous source. In the former case 
visibility was effected by the luminosity 
of the intervening medium. In the latter 
case the most luminous point was obvi- 
ously the direction of the light. 

One point that had early been appreci- 
ated in marine lighthouse work, but had 
still to be appreciated in aircraft work, 
was the utility of concentrating light 
within a small angle, and then causing the 
light to move in order to be visible in 
any part of the area at some interval of 
time. While recognising the difference 
in the conditions occurring in the case of 
aircraft, he still thought that the desira- 
bility of using an intermittent and concen- 
trated light deserved attention. It was 
recognised that an intermittent light 
would often be detected by a sensitive 
eye, whereas a steady light would not ; 
this was <\vv partly to the dark intervals 
increasing the sensitiveness of the eye, 
and partly to the fact that more 
energy was concentrated into the beam 
than when radially dispersed. 

Mr. T. E. Ritchie remarked that in 
nocturnal aviation the point of view of 
the passenger, as well as the pilot, had to 
be considered. This aspect had not, in 
his opinion, received sufficient attention 
hitherto, but if passengers were to feel 
safe and comfortable it was necessary to 
provide ample illumination in their 
quarters, in contrast with the darkness 
outside. He also thought that it would 
add materially to their feeling of comfort 
and safety, if wide angle projectors were 
used at landing points, in such positions 
that the machines came in at right angles 
to the beam. Projectors of this type 



would also be exceedingly useful in 
facilitating the embarkation of passengers 
and goods and the departure of large 
machines, as well as in the actual landing 
and disembarkation. 

Colonel Gold, of the Meteorological 
Department at the Air Ministry, remarked 
that under certain conditions flying at 
night might be safer than flying by day. 
A slight fog would often be sufficient to 
obscure the ground completely when the 
illumination came from above the fog 
as in the daytime, and yet might be suffi- 
ciently transparent to permit lights on the 
ground to be visible through the fog at 
night. The question of atmospheric con- 
ditions was naturally a most important 
one in either case, and there seemed room 
for experiment on the appearance and 
distance of visibility of lights seen through 

Mr. P. J. Waldram suggested that a 
point of some importance was a precise 
definition of the term " glaring " as 
applied to navigation lights. So far as 
the observation of distant lights was con- 
cerned, it appeared that visibility de- 
pended mainly, if not entirely, upon 
contrast ; a light mist or fog interfered 
with visibility not only because it obscured 
the light, but also because it diffused it, 
forming a luminous halo and reducing the 
sharp contrast. It might also prove 
that colour, by affording an additional 
source of contrast, was an important 
element in visibility, as distinct from 

Mr. Harrison had referred to the com- 
plexities introduced by the necessity of 
designing lighthouses to give uniform 
light within a large solid angle as com- 
pared with the beam covering the narrow 
horizontal range usual in marine lighting. 
A further difficulty would occur in de- 
signing a satisfactory form of revolving 
shutter to give a regular time period to a 
flashing or occulting light with a large 
solid angle. 

He asked for a little more, information 
in regard to the sun valve. Did this act 
automatically in the absence of sunlight, 
or would it operate in any condition as 
daylight failed ? He rather gathered 
the impression that the automatic action 

depended on solar radiation, and might 
therefore be affected by the veiling of the 
sun's rays by clouds. 

Mr. A. G. Watson, in reply to the 
question raised by Mr. Waldram, said 
that the operation of the sun valve was 
completely automatic, and was not de- 
pendent upon any form of clockwork. 
It was caused to function solely by solar 
radiation, and was capable of being so 
adjusted as to cause a light to come into 
action when there was any mist or fog 
present. As had already been mentioned 
by the author, the sun valve fitted on the 
Croydon Light operated during the recent 
eclipse of the sun. The apparatus was 
capable of being adjusted to operate 
within very narrow limits ; for instance, 
it could be set so that it would cause a light 
to commence working upon the approach 
of a heavy thunderstorm. 

Several speakers (including Commander 
Harrison) had referred to the desirability 
of causing lights used for purposes of 
navigation to flash or occult. It was fully 
appreciated that lights should have these 
distinguishing characteristics, and the 
" making " lights on the London-Lympne 
route were of the revolving types. Such 
lights were highly efficient, as the lens 
was so designed as to project a powerful 
beam over a few degrees only, instead of 
a weak one visible through 360°, as 
occurred with a stationary light. The 
revolving light, however, produced a 
beam having only from 2^° to 5° of 
vertical divergence, so that an observer 
approaching the light at a normal flying 
height might pass above and out of the 
beam whilst still a long way from the light. 
Therefore, it became necessary to make 
provision for light to be distributed from 
the lens in such a manner that it was 
available to an aviator through the whole 
vertical arc of 180°. 

In this direction it was necessary not 
only to consider the power of the light. 
but its distribution, which must be even 
and homogeneous throughout, so that the 
intensity falling upon the eye of an 
observer did not appreciably vary from 
the time that he passed out of the main 
beam till he was immediately over the 
light. The design of such an arrangement 
of optics as would do this was by no 
means an easy matter, but tin' difficulties 



were not insuperable ; on the contrary, 
it appeared that a very satisfactory 
solution of the problem had been found. 

Lieut. -Colonel C. H. Silvester Evans 
(communicated) : With reference to 
Lieut. -Colonel Blandy's paper on "The 
Use of Light as an Aid to Aerial Navi- 
gation,'" the difficulties encountered in the 
use of searchlights on landing grounds 
prompt me to make the following obser- 
vations, with regard to glare and shadows 
from searchlight beams :— 

More uniform distribution of light 
would result in a reduction of glare and 
shadow, and bearing in mind that the 
plan of the beam also serves a landing 
purpose other than illumination of the 
ground, it is thought that a greater 
number of 24-inch projectors, disposed in 
such a manner as to give a wide broad 
arrow in plan of the beam would give 
better general illumination and less glare 
and shadow, whilst still serving as an 
indication of wind direction on the 

The increased number of projectors 
would be met in a large measure by the 
lower initial cost of a 24-inch projector, 
and the use of three at a time would be 
compensated for to a huge extent l>y the 
lower running costs. 

A Yorke electro- magnetic arc control 
fitted on each lamp woidd further increase 
the amount of light with no increase of 
running costs. 

Cheap devices exist for fitting to 
searchlight projectors, for the reduction 
of direct glare, which have proved of 
considerable service, and it is thought 
these might be used particularly advan- 
tageously on the searchlights used on 
landing grounds. 

The use of searchlights for cinema work 
was early found to be fraught with 
troubles, due to glare and shadow, but 
this has largely been overcome, and in 
many cases completely so, and the 
solution in the case considered should not 
be far to seek. 

Major J. P. Ashley Waller (com- 
municated) : I wish to congratulate the 
author on his remarkable powers of des- 
cription and compression which have 
enabled him to condense a complete sum- 
mary of the work done in this field of 

engineering into a paper which did not 
take more than an hour to read ; and 
equally to compliment the Illuminating 
Engineering Society on having once more 
taken the lead in what in effect amounts 
to a new branch of science. 

With regard to the lights carried on 
aircraft as navigation lights, it seems clear 
that, owing to the high speed at which 
aerial navigation is conducted, the range 
of such lights is fixed at a dangerously 
low limit by the International Convention. 
Taking Colonel Blandy's rate of approach 
of 3*3 miles per minute, and remembering 
that aircraft have to be navigated in a 
three-dimensional field, it would seem 
imperative that every effort should In' 
made to increase the range of these 
navigation lights to the utmost and to 
fix, if possible before night flying becomes 
in any degree general, the limits of 
visibility at at least twice those laid down 
at present. Even with a Comparatively 
small volume of night traffic at such air 
ports as ( 'roydon or Le Bourget, adhesion 
to the present low ranges of navigation 
lights would appear to court disaster. 
The whole question is of course bound up 
with that of weight, but surely, in the 
case of night-flying machines, adequate 
light ranks second only to engine re- 
liability as one of the primary essentials 
for commercial success. 

The author's remarks concerning special 
high-power 12- volt filament lamps de- 
signed by the Research Department of 
the Air Ministry are most interesting, 
and it would be gratifying to know that 
it was proposed to publish a description 
and report on the tests of lamps of this 

With regard to the illumination of the 
ground on aerodromes themselves, it 
would be interesting to know what 
practical objection there is to fitting 
floodlights of some description or another 
at the centre instead of at the outskirts 
of the landing ground. It has always 
appeared to me that insufficient considera- 
tion has been given to the question as to 
whether it would not be better in all 
respects to lay out an aerodrome with all 
buildings at the centre instead of at the 
sides, and certainly from the point of 
view of floodlighting an aerodrome it 
would be obviously much cheaper to 
effect this from a central point than from 



the edges of the ground. It would, of 
course, be impossible, owing to financial 
considerations to change the existing 
aerodromes in respect of the position of 
sheds, &c, but it would seem not im- 
possible to fit batteries of floodlights at 
the centre of existing grounds, nor would 
there be any more danger to machines 
flying or running into these than into 
erections installed at the side of the 

The use of sun-valves for controlling 
beacon lights of one kind or another is, of 
course, of not very recent date in marine 
lights. It would be interesting to know 
whether this type of control is generally 
considered to be more reliable than the 
automatically-varying self-winding clock- 
work type in use on a number of marine 
buoys. The latter at first sight give the 
impression of being the less delicate 

Turning to aerial lighthouses properly 
so-called, it would be of great value to 
those interested in this branch of engineer- 
ing if the complete statistics of atmo- 
spheric absorption at varying degrees of 
elevation mentioned in Colonel Blandy's 
address could be published. My ex- 
perience is that there is a very consider- 
able difference in the method of calculating 
ranges and intensities of such lighthouses, 
and if reliable standards could be obtained 
from practical observation, many doubt- 
ful points would be cleared up. My 
personal opinion is that aerial lighthouses 
of less than the third order are a mistake, 
both from the point of view of safety and 
of that of economy. A large light has 
undoubtedly a range which frequently 
exceeds the theoretical figures, owing to 
reflection from clouds, &c. ; in populated 

districts it is much less easily confused 
with the other land lights, and it is bound 
to have greater penetration in ground 
mists than the smaller types. The 
argument put forward in favour of a 
number of smaller lights as opposed to 
the big ones is that if the atmosphere lias 
a lot of cloud or mist in patches, it is un- 
likely that all of a number of lights will 
be obscured simultaneously ; but it 
seems to me that it is equally unlikely for 
a large light to be obscured in all directions 
at once, and the reflected light from a 
large light produced by beams through 
thin patches in the mist or clouds would 
be apparent in practically any weather. 
Again, the pilot of an aircraft catching 
fleeting glimpses of one small flashing 
lighthouse through a hole in the clouds 
would find it difficult to identify the 
particular light seen out of a number 
which he knew might be seen in that 
vicinity, whereas if only one light was 
installed covering the whole area no such 
mistake could be made. Where misty 
conditions of the atmosphere are not so 
prevalent as, say, in Egypt or Mesopo- 
tamia, the single large light has other 
obvious advantages over a more numerous 
and smaller type of light. 

In this connection Colonel Blandy's 
notes on distances at which certain 
marine lighthouses have been seen from 
the air are of interest, and no doubt 
arrangements will be able to be made in 
the future with Trinity House, whereby 
selected marine lights may be modified 
to give light up to large angles above the 

(Col. Blandy's reply to the above discus- 
sion trill appear in our next issue. En.) 


By F. E. Lamplough, M.A. 
extinguishing of the lighting of aerial routes for the guidance 

The automatic 
light of an unattended lighthouse so as 
to avoid wasting light during the day- 
time has received attention for many 
years past. The problem has become 
of great importance in the last two or 
three years, owing to the urgent necessity 
of economising where practicable in 
the cost of oversight of marine lights, 
and owing to developments in the 

of aircraft, indication of wind direction, 
and of obstacles. 

Where frequent oversight of such 
lights is possible without undue expense, 
a clockwork mechanism is often used, 
as, for instance, in the lighting of street 
lamps. Even when a light is to be left 
unattended for months, clock-work 
mechanisms may be used in latitudes in 



which there are no great variations in 
the times of sunrise and sunset. If. 
however, the reliable maintenance of 
such a light is a vital necessity and not 
merely a convenience or comfort, the 
mechanism must be of a dual character 
for safety, thus greatly increasing the 
complexity and expense of the appa- 

The most obvious idea which su - 
itself to the physicist in considering this 
problem is the use of selenium cells, 
sensitive to Light. Owing, however, to 
a variety of causes, such as fatigue of 
the selenium, unreliability of contact- 
making devices, deterioration or short- 
circuiting of batteries, such contrivances 
are only to be trusted in conditions 
under which chick-work devices would 
furnish a cheaper solution of 1 he problem. 
We have, therefore, to fall back- on 

devices which do not involve the use of 

Hitherto the West known of such 
devices is the " Sun- Valve " of the 
Aktiobolagel ( iasaceumulator of Swelen. 
This apparatus, which was designed by 
Mr. Dalen, makes use of the expansion 
of a rod when heated by sunlight, direct 
or diffused, [n order that general changes 
of temperature shall have no effeel on 
the apparatus, the movement which closes 

the gas valve is brought about by the 
difference in temperature which arises 
when blackened and gilded rods are 

exposed to radiant heat or sunlight. It 
seems at first sight that such a difference 
of temperature would cause almost 
infinitesimal relative expansion, and we 
may admire the man who was first hold 
enough to put the method to the test. 
Quite a considerable difference of tem- 
perature is, however, set up in sunlight 
and with suitable methods of magnifying 
the movement the requisite effect may 

be obtained. 

This device has been on the market 
nearly II years and has received such 
wide publicity that further description 
is unnecessary. 

A very recent solution of the same 
problem has been achieved by the con- 
trivance devised by the author for 
Messrs. Chance Brothers, of Birmingham, 
for use in conjunction with their marine 
and aerial lighthouses, 

This " Light- Valve " (fillers from the 
expansion device in an important 
particular, namely, that there is large 
movement of the working parts, thus 
allowing very considerable reduction, 
instead of magnification, of movement 
by a lever system, working at great 
mechanical advantage. Tin- apparatus 
can lie made very sensitive without 
sacrificiim reliability. 

One of these light-valves, used in con- 
junction with a small marine light, 
was given a test during the whole of 
L921 in unfavourable conditions in the 
Lighthouse Works of the firm mentioned. 
During the whole of this time the light- 
valve was not touched or adjusted in 
any way. and the performance of the 
acetylene light controlled by it was 
recorded throughout the year by an 
electrical device working in conjunction 
with a thermo-COUple placed near the 
acetylene flame. Although this test was 
earned out nearly in the heart of the 
Black Country, under atmospheric con- 
ditions very different from those met 
with on the coast, on no day in the year 
did the valve fail to extinguish the light, 
and an average saving of gas as high as 
42 per cent., out of a maximum of 50 per 
cent., was registered. 

In the light-valve, volatile liquid and 
vapour of the liquid are contained in 
two connected bulbs which are sup- 
ported on a carrier. This is free to rock 
on pivots and is connected by levers to 
the valve itself. One of the bulbs is 

blackened and the other left transparent. 

The blackened bulb, oven in compara- 
tively weak daylight, reaches a tem- 
perature sufficiently in excess of the 
other, say, l-5th to l-10th of a degree 
centigrade, to cause appreciable relative 
increase in the vapour pressure of the 
liquid. A head of liquid therefore 
develops in the transparent bulb by 
transference of liquid from the blackened 
bulb, and the carrier is thereby caused 
to rock over and close the valve. 

As in many apparently very simple con- 
trivances, difficulties not evident to the 
casual observer had to be surmounted, 
such as the complete exclusion of air 
from the bulbs and compliance with 
other important physical considerations. 

[Some illustrations of this Light- Valve will 
appear in our next issue. — Ed.] 




[At the request of many of our readers we have extended the space devoted to 
this Section, and are open to receive for publication particulars of interesting 
installations, new developments in lamps, fixtures, and all kinds of apparatus connected 
with illumination. 

The contents of these pages, in which is included information supplied by the 
makers, will, it is hoped, serve as a guide to recent commercial developments, and we 
welcome the receipt of all bona-fide information relating thereto.] 


In what follows we are giving a short 
account of some recent examples of 
floodlighting, based on information 
afforded by leading manufacturers. This 
method of lighting is familiar in the 
United States and is now being applied 
in this country. 

Further developments will be watched 
with interest. 

Floodlighting at Croydon. 

Floodlighting is exciting much interest 
in this country, and there are certain 
details of importance which deserve study. 
One should, for example, obtain a 
sufficiently wide polar curve to ensure 
uniformity of lighting over the whole 
area. It happens in many cases that it 
is only possible to place the projectors 
close to the buildings, and unless the 
distribution of light is satisfactory the unit 
may not possess sufficient covering power 
to ensure the uniformity of illumination 

The accompanying photograph shows 
an installation at Messrs. Allder's premises 
at Croydon, the scheme being carried out 
by Messrs. J. & T. Robinson, Electrical 
Contractors, of Croydon, in collaboration 
with the Holophane Company. Five 
units equipped with 200-watt gas- 
filled lamps, and Holophane F.150 
Reflectors, are mounted horizontally in 
a trough placed on each side of the 
building. The angles and setting of 

the units have been carefully calculated, 
and adhered to by the contractors. It 
will be noticed that the architectural 
features of the building stand out clearly 
and the lighting of the entire surface of 
the stonework is extremely uniform. 

Another feature worthy of mention is 
the few points needed to produce such 
a result, with the economical energy 
consumption of 2"4 units per hour. 

Fig. 1. — Showing Holophane floodlighting 
installation at Messrs. Allder's premises at 



Floodlighting at Selfridge's. 

It has been remarked as curious that 
the idea of " floodlighting " the exteriors 
of buildings of distinction has not yet 
made much headway in this country, 
but in the near future, when considera- 
tions of economy are less acute, it will 
doubtless become more familiar. 

An interesting illustration of the 
possibilities of the method is afforded by 

ing illustration gives a good idea of 
the result. The effect of this isolated 
instance of floodlighting is to cause the 
building to " stand out " in a striking 
manner and there is no doubt that such 
7 net hods of concealed lighting furnish a 
valuable aid to public lighting in the 
streets. This interesting departure will 
doubtless be followed bv other con- 

A view of Selfridge's showing the effeet of the floodlighting 

the new ins! allal ion at Selfridge's, carried 
out by the Qeneral Electric Co., Ltd., to 
whom wc are indebted for these par- 

The lighting is effected by 400 watt 
gas-filled lamps with specially designed 
filaments, equipped with parabolic re- 
flectors. The sources are concealed from 
view, the facade of the building being 
brightly illuminated. The accompany- 

A booklet issued by the Welsbach Light 
Co., Ltd., remarks that just 35 years have 

elapsed since the first exhibit of the 
Welsbach Light in 1887. The process of 
manufacture of Welsbach mantles, in- 
volving 22 distinct operations, is described 
and attention is drawn to the fact that 
this is an " All -British " industry. Con- 
siderable reductions in price are also 



INDEX, February, 1922. 

Editorial. By L. Gaster . . 

illuminating engineering Society— 

(Founded in London, 1909) 

Account of Meeting on January 31st, 1922 

The Use of Light as an Aid to Aerial Navigation. By Lt.-Col. L. F. 

Blandy, D.S.O. 

Dicussion — The Chairman (Major-Gen. Sir Frederick Sykes, 

G.B.E., K.C.B., C.M.G.)— Col. Mervyn O' Gorman -Major-Gen. 

Sir Sefton Brancker, K.C.B. — Sir Acton Blake (Deputy 

Master of Trinity House)— Mr. Haydn T. Harrison— Mr. T. E. 

Ritchie — Col. Gold (Meteorological Dept., Air Ministry) — 

Mr. P. J. Waldram— Mr. A. G. Watson— Lieut.-Col. C. H. 

Silvester Evans — Major J. P. Ashley Waller 

Light- Valve, The, by F. E. Lamplough 

Reviews of Books 

Topical and Industrial Section (Floodlighting) 






An interesting sign installation employing 
B.T.H. Floodlight Projectors has been 
caniecl out at the Maypole Margarine 
Works, Southall. The sign is a painted 
board — white letters on a black ground 
— measuring 100 feet by 6 feet, illumin- 
ated by three projectors (type 793), each 
containing a 500-watt Mazda gashlled 
projector lamp. The three projectors 
are fixed 50 feet from the sign. 

Fig. 2.— Showing installation of B.T.H. floodlighting projectors at 
the Maypole Margarine Works, Southall. 

The beam of light from a projector is 
of circular section, and to light a 100-feet 
sign six feet high with three such beams 
would not be practicable. To have the 
necessary beam, 33 feet in diameter, 
would entail a loss of 131 feet <>f useless 
light above and below the sign, and a 
correspondingly low intensity on the 

The difficulty was overcome by the use 
of special spreading glass fronts which 
produce an elliptical 
beam. It will be seen 
from the illustration, 
taken by the light of 
the projectors, that there 
is no waste and that 
practically all the light 
is confined within the 
limits of the sign-board. 

The Maypole sign 
serves to illustrate the 
advantages of floodlight- 
ing. Even and brilliant 
illumination is obtained 
without any visual dis- 
comfort to the observer, 
which is a point worthy 
of consideration in adver- 
tising. For the particu- 
lars given above, we are 
indebted to the British 
Thomson - Houston Co., 
Ltd. (77, Upper Thames 
Street, E.C. 4). 




Wk have received from the Scientific 
Electrical Co. (The Piatt, Putney, 
London) particulars of a new type of 
flasher which has interesting features. 
The chief novelty involved is the use of 
a permanent magnet. In the simplest 
small types a permanent bar magnet is 
used. Parallel to this is a strip composed 
of metals of unequal coefficients of 
expansion heated by an insulated spiral 
of copper wire. The heating effect of this 
spiral causes the strip to be bent towards 
the pole of the magnet by which it is 
ultimately attracted and held, in so doing 
short circuiting the spiral and allowing 
the strip to cool. Accordingly it pre- 
sently drags itself away from the magnet, 
the spiral coil again comes into operation, 
and the whole process begins again. 

The advantage claimed for the use of 
the magnet is that a relatively long and 
definite break is secured, as the force of 
attraction increases very rapidly with the 
proximity of the strip to the magnet, 
There is. therefore, none of tin- uncertain 
trembling effect which would otherwise 
he apt to occur, and w hich may prejudice 
flashing operations involving a regular 
sequence of actions. In addition the 
sensitiveness can he varied within wide 
limits by adjusting the normal distance 
between the tungsten contacts, a dark 
period of as much as half a minute being 

On account of the small voltage drop 
in the flasher it can be operated on 
pressures as low as 12 volts. The smallest 
type is suitable for dealing with circuits 
up to 4(>i» w atts, but larger models capable 
of dealing with loads up to 5,000 watts 
are also listed. The flashers have been 
used with advantage for operating the 
new " discharge " lamps based on the 
luminescence of neon gas and consuming 
Only 5 watts and for the automatic ex- 
tinction of heating appliances when the 
boiling point of water is attained. The 
flasher lends itself very rapidly to two- 
way operations, i.e., the smooth lighting 
up of two alternative sets of lamps in 


On Saturday, February 18th, a party 
consisting of members of the Association 
of Engineers-in-Charge visited the 
Benjamin Electric Limited's, works at 
Tottenham, where the various manufac- 
tures and methods were explained. The 
party, which numbered over 30, made an 
explanatory tour of the works, and in 
addition attended a short lantern lecture 
on Industrial Lighting, which was much 


The Practical Electrician's Pocket Book 
(S. Rentell & Co., London, 1922, 3s. 
net. ; p.p. 558 + lxxxiii). 

We have pleasure in recording the 
appearance of the 24th edition of the 
"Practical Electrician's Pockel Book. 

The contents of this familiar publication 
will be known to our readers from pre- 
vious reviews. It covers a very wide 
ground and the present edition has 
undergone general revision; certain 
sections have also been completely re- 
written. The section on illumination 
and photometry is exceptionally com- 
plete, considering the necessity for com- 
pression, and has evidently been recently 
brought up to date. The matter devoted 
to wiring and switches also seems to be 
dealt with on practical lines, and is 
greatly aided by the liberal use. of illus- 
trations. The tallies, a^ usual, arc a 
useful feature. 

In view of the large amount of con- 
densed information to v be found in the 
Diary, and the great increase in the 
costs of paper and printing that has 
occurred since pre-war days, the price 
appears moderate. 












illuminating Engineering Society. 

(Founded in London, 1909.) 



Tel. No. Victoria 5215. 


Industrial Lighting: Idea! Requirements (legislative and otherwise) and 

Practical Solutions. 

It will be recalled that, following the issue of the First Interim Report 
of the Home Office Departmental Committee on Lighting in Factories 
and Workshops in 19 15, the report was fully discussed at two subsequent 
meetings of the Society. This step was found useful, both in enabling the 
contents of the report to be commented on and more clearly understood in 
all its aspects ; and also in giving, through the accounts of the discussion 
that appeared in many technical journals, wide publicity to the report in 
industrial circles. 

The precedent was accordingly followed at the meeting of the Society 
on February 28th, when a paper was presented by the writer, special 
reference being made to the Second Interim Report of the Committee, 
issued last year. Mr. D. R. Wilson, a member of the Home Office Committee, 
in opening the discussion, invited those present to criticise the report, so 
that the Committee might have an opportunity of considering possible 
modifications, before the stage for taking statutory action was arrived at. 
We have reason to believe that several useful suggestions originated as a 
result of the discussion, notably in regard to the clause in the Report dealing 
with avoidance of glare. 

A feature of interest in the paper is the reference to the admirable 
revised code of industrial lighting, recently issued by the Illuminating 
Engineering Society in the United States. This reveals a close agreement 
between the aims pursued in both countries. The actual "rules" are 
reduced to the smallest possible compass and simplicity, but are supple- 
mented by very comprehensive explanatory matter and by a section 


explaining the benefits of good industrial lighting. There is a broad classifi- 
cation of the orders of illumination desirable for various classes of work, 
supplemented by a much more detailed list of processes and intensities 
required, in the explanatory section. It is to be noted that the values 
desirable in practice are considerably higher than those prescribed as legal 
minima. Similarly the simple requirement for avoidance of glare, is 
supplemented by a well considered series of tables and diagrams showing 
how various sources can be classified in terms of glare, and their positions 
in rooms defined accordingly. 

The further recommendations made in the Second Interim Report 
of the Home Office Committee in this country are of considerable importance 
to illuminating engineers and to the industry as a whole. There was a 
general recognition expressed in the discussion that these recommendations 
could readily be complied with by using modern illuminants and illumin- 
ating apparatus, and that their application would remove the worst cases of 
unsatisfactory lighting, and raise the general standard of illumination in 
factories considerably. Indeed, it is understood that recently acquired data 
support the view that there has been a substantial advance in the values 
of illumination used in many trades, since the data on this subject were 
published in the 1915 Report. 

We find also a consensus of opinion that the Home Office Committee has 
acted wisely in first prescribing values of illumination necessary in the 
interests of safety and general convenience, leaving the actual values 
desirable for the carrying on of specific industrial processes to be settled 
by conference with the trades concerned. Conditions of vision required for 
a particular trade play an important part in the selection of workers. The 
eyesight of workers should be ample for the process, and the illumination 
provided suitable for the work undertaken. No doubt determinations 
on this basis will take time and may naturally involve some expense. 
But it is surely best that the method of selection should be thoroughly 
scientific and authoritative, so that measures proposed may carry conviction 
and meet with general acceptance. We trust that, when the present 
demands for economy have become less stringent, facilities will be given 
to the Industrial Fatigue Research Board — which, largely through the 
efforts of its energetic secretary, Mr. D. R. Wilson, has already done such 
useful work — enabling it to extend its researches on industrial lighting. 

In the United States, as in this country, we observe with pleasure the 
recognition that any legislation on factory lighting, whilst checking abuses, 
must involve no hardship — must meet with general acceptance as being 
devised in the interests of both management and employees. The con- 
siderable number of bodies, representative both of employers and labour, 
that are co-operating with the Illuminating Engineering Society in that 
country in framing and revising the code furnishes an analogy with the 
methods proposed by the Home Office Committee in this country. The 
judicious and sympathetic treatment of the subject by the Home Office 
deserves every recognition, and the acknowledgment by Mr. Graves, 
H.M. Chief Inspector of Factories, in his address at the Annual Dinner 
(see p. 94) of the assistance derived from the Illuminating Engineering 
Society, is a gratifying testimony to the work it has done in advancing 
the standard of industrial lighting in this country. 

It is satisfactory to observe the agreement in method and principle 
between the recommendations made in this country and the United States, 
which should help to pave the way for the international treatment of the 


Inadequate Lighting as a Cause of Miners' Nystagmus. 

It will be recalled that a discussion before the Illuminating Engineering 
Society on February 24th, 1920,* revealed a consensus of opinion among 
experts that inadequate lighting in mines, besides being a contributory 
cause of accidents, was the main factor in causing the disease of the eyes 
known as miners' nystagmus, by which large numbers of workers have been 
incapacitated yearly, leading to much suffering and economic loss. The 
work of Dr. T. L. Llewellyn, who read the introductory paper on this 
occasion, contained striking data in support of this conclusion, which has 
been confirmed by the researches of Dr. Stassen, in Liege, also recorded 
in this journal. On that occasion we expressed the hope that researches, 
correlating measurements of illumination in mines with data on defective 
vision of miners, would be continued. This has been done by a Committee, 
consisting of Prof. J. S. Haldane, Dr. E. L. Collis, Mr. G. H. Pooley, Dr. 
W. H. R. Rivers and Dr. T. L. Llewellyn, formed by the Medical Research 
Council to inquire into the causes of miners' nystagmus. The report 
of the Committee f fully confirms the conclusions tentatively set out at the 
discussion of the Illuminating Engineering Society. The Committee are 
unanimously of opinion that " the essential factor in the production of 
miners' nystagmus is deficient illumination." Other factors such as 
position during work, accidents, alcoholism, malnutrition, hereditary 
indisposition, and errors of refraction, are also of consequence. The deficient 
illumination is due to (a) the low illuminating power of safety lamps in 
common use, (b) the distance at which these lamps have to be placed from 
the objects observed, and (c) the great absorption of light by coal and 
coal-dust covered surfaces, or by coal-dust and dirt deposited on lamp 
glasses. Workers at the coal face are more affected than other under- 
ground workers, apparently owing to the unrelieved blackness of the coal. 

Incapacity due to nystagmus is rare in coal mines with open lights, 
and the Committee recommend that everything possible should be done to 
make the standard of illumination equal to that prevailing in mines of this 
nature. This can be effected by increasing the candlepower of the lamps 
to about two or three candles, or by the use of lights capable of being fixed 
on the miner's head or other convenient position, so that the light is auto- 
matically brought nearer to the working area, and does not impair clear 
vision by shining in the workers' eyes. At parts of the pit other than the 
coal face the visibility of objects can be greatly increased by whitewashing, 
as well as the stone-dusting now obligatory for the prevention of explosions. 

These conclusions are supported by a wealth of evidence and by reference 
to sources of information, amongst which the discussion before the Illumin- 
ating Engineering Society is quoted. We feel sure that this authoritative 
endorsement of the part played by inadequate lighting in causing defects 
of vision among miners will lead to energetic efforts to make use of the 
improvements indicated, and we need not say that the Illuminating 
Engineering Society will gladly co-operate in efforts to ensure this being done. 

Thanks are due to Dr. T. Lister Llewellyn, the Secretary of the Com- 
mittee, whose pioneering work was largely responsible for exciting interesl 
in this subject, and to the Medical Research Council, which we hope will 
take an interest in and support the Society's endeavours in other useful 
researches involving the effect of light on the eye. 

* Illum. Exg., March 1920. 

j First Report of the Miners" Nystagmus Committee, issued by the Medical Research 
Council, published by H.M. Stationery Ofrice. is. 6d. net. 


A Visit to Roumania. 

In the years preceding the war it was an essential part of the programme 
of the Illuminating Engineering Society to keep in touch with developments 
abroad, and the writer, on several occasions, visited the Continent and 
America with a view to meeting leading authorities on illumination. It 
is pleasant to feel that some progress towards the resumption of these 
relations has already been made — one notable event being the first technical 
session of the International Illumination Commission held in Paris last July, 
at which most of the countries of Europe were represented. It should not 
be overlooked that there are now countries developing in the south-east 
of Europe, in several of which there appear to be prospects of progress in 
illuminating engineering. 

Among the countries in the Balkans, none is of greater interest than 
Roumania, to which the writer, as Hon. Gen. Secretary of the British 
International Association of Journalists, had the pleasure of paying a visit, 
at the invitation of the Roumanian Government last Autumn. The party 
consisted of four representatives of the Association, namely, Sir Harry 
Brittain (President), Mr. Walter Jerrold (Hon. Treasurer), Mr. Walter Lee, 
and the writer. 

To one familiar with Roumania, it was most interesting to take note of 
the changes occasioned by the war. Roumania has emerged with an area 
and population vastly greater than in the past, and as the inhabitants are 
broadly similar in race and religion, there is reason to expect that it will 
develop into a homogeneous nation. 

The natural resources of the country are considerable. Its oil industry 
was of great importance prior to the war, and is now recovering from the 
destruction that took place at the time of the entry of hostile forces. There 
are valuable mineral deposits, particularly in the new and little developed 
Transylvanian area now added to Roumanian territory. 

During their visit the party received every assistance from the authori- 
ties, and were honoured by a reception and luncheon at the Royal Palace at 
Sinaia. The writer, unfortunately, was taken seriously ill at this time, and was 
unable to attend, but he was subsequently granted an audience with H.M. 
the King of Roumania, who was much interested to hear of developments 
in England. On this occasion, the opportunity was taken to give some 
account of the illuminating engineering movement in this country, in which 
His Majesty expressed much interest, especially in regard to legislation on 
factory lighting. In conversation with leading authorities on education 
the writer also referred to the importance of adequate lighting in schools. 
He found everywhere a sympathetic interest in this work, and was asked to 
keep the authorities informed of further developments that might be made 
the basis of action in Roumania. As would naturally be expected in a 
developing country lighting conditions are varied. In some of the chief 
cities the public lighting, and the conditions of illumination in important 
buildings, will bear comparison with those in this country. In the smaller 
towns, however, arrangements are more primitive, and there is room for 
considerable development. Both electric and gas lighting are to be found 
at important centres. The cordial and sympathetic interest expressed 
both by His Majesty and by leading authorities makes one feel that 
Roumania will eventually become one of the centres for the study of 
illuminating engineering in the Balkan States, of which she is a leader. 





£be Slluminating Engineering Society 

(Pounded in London, 1909.) 

The Illuminating Engineering Society is not, as a body, responsible 
for the opinions expressed by individual authors or speakers. 



(Proceedings at the meeting of the Society held at the House of the Royal Society of Arts, 
18, John Street, Adelphi, London, W.C., at 8 p.m., on February 28th, 1922.) 

A meeting of the Society took place 
as stated above, the Chair being taken 
by Mr. J. Eck. 

The minutes of the last meeting 
having been taken as read, the Hox. 
Secretary read out the names of new- 
applicants for membership as follows : — 
Ordinary Members. 
Beauchamp, J. W. 

ensued, in which Mr. D. R. Wilson 
(Industrial Fatigue Research Board), 
Mr. J. Herbert Fisher, F.R.C.S. (Pre- 
sident of the Ophthalmologic^ Society), 
Mr. W. R. Rawlixgs, Mr. J. W. T. 
Walsh, Mr. P. J. Waldram, Mr. L. M. 
Tye, Mr. J. G. Clark, Capt, E. Stroud 

Tweedie Smith, Captain L. 

Sugg, Philip U. 

Ashley Waller, Major J. P. 

Pye, F. P. .. 

Director of the Electrical Development 

Association, 15, Savoy Street, Strand, W.C. 
Managing Director of the Rawlplug Co., 

Gloucester House, Cromwell Road, S. 

Chairman and Managing Director of Wm. 

Sugg & Co., Ltd., Regency Street, 

Westminster, S.W.I. 
Lighting expert and naval architect, 26, 

Audrey House, Ely Place, London, E.C. 

Student at Faraday House, Southampton 
Row, London, W.C.I. 

The Hon. Secretary also read out 
the names of those announced at the 
previous meeting and these gentlemen 
were formally declared members of the 

The Chairman then called upon Mr. 
L. Gaster to open the discussion on 
"Industrial Lighting: Ideal Requirements 
(Legislative and otherwise) and Practical 
solutions." An interesting discussion 

and Mr. S. B. Chandler took part. 

Mr. Gaster, having briefly replied, a 
vote of thanks to the Author and Chair- 
man terminated the proceedings, after 
which the Chairman announced that 
the next meeting would be held on 
March 28th, when there would be a 
discussion on "The Lighting of Public 
Buildings, Scientific Methods and Archi- 
tectural Requirements." 



Industrial Lighting : Ideal Requirements (Legislative and 
otherwise) and Practical Solutions. 

By L. Gaster, F.J.I. 

(Presented at the meeting of the Uluminatins Engineering Society held at the House of the 
Royal Society of Arts, 18, John Street, Add phi, London, W .('., at 8 p.m., on Tuesday, 
February 28th, 1922.) 


It is generally admitted that great 
advances have been made in our know- 
Ledge of industrial lighting requirements 
during recent years. The introduction 
of simple instruments for measuring 
illumination has given us an insight into 
the values of illumination customary in 
different factories. Researches have been 
conducted into the causes of glare and 
its prevention, the best ways of elimina- 
ting troublesome shadows, and the special 
requirements of certain industrial pro- 
cesses. We stand in a very different 
position from what we did when the 
Society commenced its work 13 years ago. 

These advances paved the way for the 
preparation of official recommendations, 
such as those contained in the First 
Report of the Departmental (Home 
Office) Committee on Lighting in Fac- 
tories and Workshops in this country 
(1915)* and supplemented in the Second 
Report issued last year (1921 ).f In the 
United States there are now seven codes 
of industrial lighting in existence, all 
based on principles commonly accepted 
by experts. 

Ideal Requirements. 

The natural course is, firstly, to form 
some conception of ideal factory lighting : 
secondly, to see how far such conditions 
can at present be obtained in practice. 
Ideal industrial lighting can only be very 
broadly described. It should be such as 
to enable work to proceed at night with 
the same ease and convenience and 
safety to workers as exist under the best 
daylight conditions ; indeed, in view of 
the variability of daylight, one might 
conceivably attain even better conditions 
in certain cases. General experience, 
aptly summarised in the reports of the 
Home Office Departmental Committee, 

* Illum. Eng., Sept., 1915. 
f Illum. Eng., Oct., 1921. 

indicates that for ideal requirements 
there are four main conditions to be 
satisfied, namely: (a) Sufficient illumina- 
tion ; (b) Constancy and Uniformity of 
illumination over the working area ; (c) 
The placing and shading of lights so that 
no inconvenience and prejudicial effects 
are experienced from '" glare " ; (</) The 
placing of Lights so as to avoid incon- 
venient extraneous shadows on the work. 
There will naturally also be special con- 
ditions to l>e fulfilled arising from the 
peculiar nature of any industrial process, 
and a form of illumination that is ideal 
for one process may be less satisfactorv 
for another. 

Practical PosaibMi 

In order to approach " ideal " re- 
quirements we must first be able to define 
them, and although we have gone some 
distance in this direction, it will natur- 
allv take time before they are com- 
pletely understood in all industries. The 
best course is perhaps to group together 
certain industries, having broadly similar 
requirements, to study them in detail, 
and to see how far this experience applies 
in other cases. Hence, the Departmental 
Committee acted wisely in first con- 
centrating attention on the engineering, 
clothing and textile industries. In aim- 
ing at securing sufficient light we must 
distinguish between the illumination 
necessary in the interests of safety and 
freedom from accidents., which has already 
been specified in the Departmental Com- 
mittee's first report, and the illumina- 
tion necessary for carrying out efficient 
work, which is a much more complex 
matter. Here again the Committee dealt 
with the most urgent and readily prac- 
ticable problem first. In the American 
codes it is customary to specify a mini- 
mum working illumination for rough, 
medium and fine operations, figures 
ranging from 1 to 5 foot-candles being 



How, it may be asked, can we ascer- 
tain what working illumination is re- 
quisite ? The most convenient plan is 
to collect statistics of prevailing values 
in existing factories ; this tells us what is 
practicable and usual, but not neces- 
sarily what is best. A more scientific 
method is to experiment with different 
illuminations, asking the workers to 
state when they consider the illumination 
sufficient for their needs, and to indicate 
when the light is diminished to a point 
where they begin to find trouble in doing 
their job. One might supplement such 
tests by records of output under varied 
lighting conditions. This has recently 
been done in Chicago, with the result 
that in some factories better illumination 
led to increases in output of 8-25 per 
cent., while in others, where the original 
conditions were very bad, increases of as 
much as 30-100 per cent, were noted. 

It is evident that the collection of such 
data means a considerable amount of 
work. When we come to consider closely 
other factors, such as avoidance of glare, 
we again meet complex problems. If we 
could devise a simple test of glare, the 
problem would be easier. Some work in 
this direction has been done, e.g., by 
judging the appearance of " after-images"' 
on the retina of the eye, by observing 
when a fine line seen against the source 
as a background appears blurred, or when 
some fine detail becomes indistinguishable 
owing to the brightness in its vicinity. 
We may also fall back on accumulated 
experience of conditions under which 
a distinct feeling of uneasiness is experi- 
enced by the normal eye owing to glare, 
and prescribe rules as to the shading and 
positions with respect to the eye of light 
sources, as was done by Weber in a con- 
tribution on this subject very early in 
the history of our Society.* 

One point has been impressed on all 
of us who have had experience of such 
researches. We must consider the vari- 
ous factors necessary for ideal conditions 
as a iv/fole. The provision of a very high 
illumination will not suffice if other pre- 
judicial elements such as glare or trouble- 
some shadows exist. This point has 
been repeatedly emphasised in the Ameri- 
can codes, and one of the latest, that of 
Oregon, accordingly adopts the practice 

* Illttm. Eng., 1910, p. 116. 

of putting schedules of illumination at the 
end of the code and a discussion of the 
other factors at the beginning. 

Let me illustrate this point by a few 
examples. One most important element 
is the reflecting power of the material 
worked upon. The original report of the 
Home Office Committee contained a 
summary of some experiments made at 
the National Physical Laboratory. Seam- 
stresses were asked to work in a room 
where the illumination could be varied. 
They were invited to say when the 
illumination seemed sufficient, first work- 
ing with light cloth and next working 
with materials of various degrees of 
darkness. It appeared from these ex- 
periments that a rough rule could be 
deduced based on a standard bright ties* 
of the material, i.e., that the product of 
the illumination provided and the reflect- 
ing power of the material should be 
constant. The conclusion is obvious, 
A degree of illumination necessary in 
sewing with white materials must be 
enormously increased when very dark 
material is handled, and according to my 
personal experience in clothing factories, 
one meets kinds of work, involving fine 
sewing with black cloth and black thread, 
which can only be economically and 
efficiently dealt with by bringing a well 
shaded light close to the work, so as to 
secure the requisite high illumination. 
Another equally important factor is 
contrast between materials used. Sewing 
with white or coloured cotton on dark 
cloth would obviously be a different 
matter from the use of black cotton with 
black cloth. The requisite illumination, 
again, is affected by contrast conditions 
in regard to the conditions of lighting 
generally. Local lighting requires to be 
supplemented by moderate general illu- 
mination to prevent excessive contrast 
between the brightness of the material 
worked on and the subdued brightness 
of the rest of the room. It appears also 
that general overhead lighting, with 
white walls and ceilings, though excellent 
for many forms of work, does not answer 
so well when dark materials are used. 
for the reason that the contrast here is 
reversed- i.e., the dark material is apt 
to appear indistinguishable in comparison 
with the greater brightness of surround- 
ing objects. 



Another very important factor is direct 
reflection of light from polished material. 
If not guarded against glare of this kind 
may make it difficult to work, even if 
the illumination provided has quite a high 
value. .Similarly the presence of im- 
perfectly screened glaring lights within 
the range of vision is apt to give rise 
to a continually increasing demand for 
more light on the work, whereas properly 
shaded lights enable the eve to get the 
fullest advantage from the illumination 

Other complexities occur in those 
cases where it is quite difficult to obtain 
the requisite illumination at the actual 
point of work, without introducing 
troublesome shadows. The lighting of 
benches equipped with rows of sewing 
machines is a case in point. Inconvenient 
shadows from parts of the machine are 
by no means easy to avoid, and conditions 
in this respect are more exacting in some 
cases than in others, depending on the 
manner in which material is handled. 
Textile factories, containing much bulk 
and complicated machinery, present 
similar difficulties as regards obtaining 
the requisite illumination at the exact 
point where it is wanted and avoiding 
awkward shadows, either from the person 
of the worker or from adjacent projecting 

Apart from the circumstances men- 
tioned above it is evident that the 
amount of illumination needed will 
depend to some extent on the familiarity 
of an operator with the process. Higher 
values might be needed in the case of 
a comparatively unskilled operator than 
for one to whom the work has become 
second nature. The illumination re- 
quired in order that the eye may be 
completely satisfied will also naturally 
vary according to the intricacy of the 
process. It is generally assumed, for 
instance, that for reading clear print 
on white paper we need at least 2-3 foot- 
candles. But an interesting investiga- 
tion conducted by Dr. P. W. Cobb, of 
the Nela Besearch Laboratory, shows 
that the speed of reading .is closely 
connected with the illumination. The 
personal factor enters into this problem 
and the average of the performances 
of a number of different observers was 
accordingly taken. Diagrams were pre- 

sented showing that speed of reading 
tended to increase with rising illumina- 
tion, the needs of the eye being appa- 
rently met by an illumination of about 
60 foot-candles on white paper, though 
a further advance of 60-100 foot-candles 
still led to an appreciable increase in 
facility of reading. 

These experiments are of interest in 
view of a report recently issued by the 
Committee on Elimination of Waste 
in Industry, of the American Engineering 
Council. The Committee collected sta- 
tistics of eyesight in a number of indus- 
tries. It is significant that of 2,906 
workers in garment-making factories 
only about 25 per cent, had normal 
vision in both eyes and only a farther 
17 per cent, normal vision in one eye. 
It is believed that these defects are 
largely due to inadequate lighting, and 
that higher values of illumination would 
have a beneficial effect. Importance 
is attached to the economic loss involved 
in faulty lighting conditions. 

A few words should also be said as to 
the advisability of proper maintenance 
and periodical deeming of lamps and 
lighting appliances, as well as of the 
window glass in a factory through which 
daylight is admitted. Mr. Clewell, some 
years ago. found that a few weeks' neglect 
in a factory might lead to a consider- 
able loss of light, and that after several 
months' neglect the illumination might 
be reduced by 30-40 per cent., owing to 
deposits of dust and dirt on lamps and 
fittings. In the case of gas lighting 
installations the desirability of regular 
maintenance by the gas companies, 
who are prepared to undertake this 
duty in a thorough manner, is evident. 
Some actual experiences of the loss in 
light arising from deposits of dust are 
illustrated in the Code of the American 
Illuminating Engineering Society. The 
diagram, which is reproduced herewith, 
speaks for itself. 

There is thus room for much further 
study to determine " ideal requirements " 
in factory lighting. But enough has 
been said to show that we have already 
learned a good deal, and the mere fact 
that we can now express our needs and 
outline the things we have still to learn, 
shows that we have progressed. 


Legislative Requirements. 

It is a tribute to the progress made in 
the study of industrial lighting, and to 
the sympathetic and enterprising attitude 
taken by the Home Office in this country 
to the problem, that the introduction into 
the Factory Acts of statutory provision : 
(a) requiring adequate and suitable light- 
ing in general terms in every part of a 
factory or workshop ; (b) giving power 
to the Secretary of State to make Orders 
defining adequate and suitable illumina- 
tion, has already received attention. 
Very wisely, the authorities have been 
content to await public recognition of 

and becomes a source of annoyance to the 
manufacturer ; if too vaguely worded 
its interpretation may give rise to trouble- 
some differences of opinion. One's aim 
should be to produce measures which are 
necessary alike to employer and em- 
ployee, as being for their benefit, and 
which aid the manager in his duty of 
providing proper illumination. Above 
all it is desirable that official information 
should be generally understood. The 
discussion of the first report of the Home 
Office Departmental Committee before 
this Society in 1915 had most beneficial 
results. It is hoped that some account 

Walk and Ceiling * 

Increase: — 
New Lamps ol g 
Proper Voltage m 

Lamps and Re- >£ 
(lectors Washed £ 

Final Intensity 

Final Intensity 


Lighting Units g 

Cleaned § 

Increase:— t* 
urnouts in Multi ■} 
light Fixtures 

Increase: — 
Walls Refinished £ 

Occasional Maintenance 

No Maintenance 

Periodic but Inade- 
quate Mainienance 

Fig. 1. — A diagram illustrating the benefits of regular cleaning and maintenance 
(Illum. Eng. Soc, U.S.A., Code of Lighting in Factories and Workshops). 

the desirability of such measures before 
making this recommendation — to follow 
the principle of " Government by Con- 

Needless to say, legislative measures 
require very careful consideration, and 
one might justly hesitate to legislate on 
many matters, on which recommenda- 
tions can confidently be made. Any form 
of " code " must be such that it can 
readily be enforced by those charged with 
the duty, and will actually prevent tin- 
most serious abuse of industrial lighting, 
and yet impose no hardship on the manu- 
facturer. If too exact and detailed it 
becomes difficult to enforce intelligently 

of the second report issued last year, will 
be equally helpful. 

Second Interim Report of the Depart- 
mental (Home Office) Committee on 
Lighting in Factories and Workshops. 

As mentioned above the first report of 
this Committee recommended certain 
values of illumination, ranging from 0*05 
foot-candles in open places up to 0*-t foot- 
candles in foundries, as desirable in the 
interests of convenience and safety, in 
view of the relation clearly established 
between inadequate illumination and the 
prevalence of accidents. The question 
of " working illumination " has not yet 



been completely dealt with, although it 
is understood that much useful informa- 
tion has been compiled, and that suitable 
values will be ultimately agreed upon by 
consultation with the representatives of 
the industries concerned. This is. again, 
in accordance with the wise policy of 
" Government by Consent." 

It also contains the following recom- 
mendation on the avoidance of glare :-■— 
Every light source (except one of low 
brightness) within a distance of 100 ft. 
from any person shall be so shaded from 
such person that no part of the filament, 
mantle or flame is distinguishable through 
the shade, unless it be so placed that the 

V ,,. , 

An«le df 
cut-off 20 . 


a. — Angle 
of cut-off 30°. 

This lighting unit will comply with the 
requirements 01 the Some Office Departmental 
Committee's Second Interim Report it hung 
in any position (provided it is uot within -i\ 
feet <>f t he operator). 

Tins Lighting unit will comply with the 
requirements in the Second Interim Report of 
the Home Office Departmental Committee, 
irrespective of its distance from the operator. 

-^^^* ^^^^ ^^^^ ^y^^ 



I'm.. ::. Showing height at which lighting units having exposed filaments must be 
placed so as to fall outside the 20° angle, specified in the section of the Second 
Interim Report of the Home Office Departmental Committee dealing with glare. 
Lighting units equipped with suitable diffusing glassware to screen the filament, 
or with reflectors the edge of which falls below the filament, could he hung at a 
lower level. 

The second report makes general re- 
commendations on " shadow " and *' con- 
stancy," namely that " adequate means 
shall be taken to prevent the formation 
of shadows which interfere with the 
safety or efficiency of any person pre- 
sent " ; and that " no light sources 
which flicker or undergo abrupt changes 
in candlepower in such a way as to inter- 
fere with the safety or efficiency of anv 
person employed shall be used for the 
illumination of a factory or workshop." 

angle between the line from the eye to 
an unshaded part of the source and a 
horizontal plane is not less than 20°, or 
in the case of any person employed at a 
distance of 6 ft. or less from the source 
not less than 30°." 

The application of this recommenda- 
tion would doubtless remove the worst 
examples of glare. Yet it imposes no 
hardship as it can readily be complied 
with in various ways. Thus, sources 
adequately shaded by diffusing glass or 



Fig. 4. — View of a Machine Room in an Iron Works at Croydon (95 ft. by 40 ft.), lighted by 
four Keith (1,500 candlepower nominal) high-pressure gas lamps, arranged down centre 
of room at a height of 25 ft. Consumption : 120 cub. ft. of gas per hour. The 
photograph illustrates the advantage of mounting lamps high op with a view to avoiding 
glare and leaving a clear view of the workroom. 

Fig. 5. — Showing local lighting of a section of a boot factory at Northampton. The 
incandescent burners, in Holophane reflectors, are 2 ft. (i in. above the work 
on the fitter's table, and furnish 12-16 foot -candles. Mantles arc completely 
screened from the eyes of operators. 



vitreosil glassware could be used any- 
where in a workroom. Reflectors, such 
as I shall illustrate, with a " cutting off " 
angle of 20° could also be used in prac- 
tically any position. Even lighting units 
with a mantle or filament located below 
the edge of the reflector can be used high 
up provided they fall outside the speci- 
fied 20° angle. 

The recommendation does not attempt 
to impose ideal conditions. It is a com- 
promise but should have a salutary effect. 

The American I.E.S. Code. 

As it is useful to compare our experience 
with that in the United States, it is 
proposed to present data relating to 
typical American " Codes " of industrial 
lighting, particularly the latest version 
of the code of the American Illuminating 
Engineering Society.* The latter crystal- 
lises American experience. The code 
itself contains only three rules dealing 
respectively with amount of illumination, 
avoidance of glare, and the lighting <>f 
exits and emergency lighting. Values of 
illumination of 1, 2, 3 and 5 foot-candles, 
according to the degree of detail discrim- 
ination involved, are proposed. These 
are clearly defined as minimum values of 
working illumination, which could be 
advantageously exceeded in practice. 

Part II. is devoted to general sugges- 
tions and explanations, and contains a 
series of values of illumination illustrating 
good modern practice, much higher than 
the minima, and ranging up to lO 20 
foot-candles. This section also outlines 
an elaborate and scientific method of 
grading sources of light according to their 
candlepower and intrinsic brilliancy 
(candles per sq. in.) and defining the 
positions in which they can be used. The 
system is based on similar fundamental 
principles to those adopted by the British 
Home Office Committee, and well de- 
serves study. 

Part III. is devoted to a general dis- 
cussion of the benefits of good lighting, 
in accordance with the practice generally 
followed in presenting industrial lighting 
codes. The aim is the same as that 
adopted in this country, to make the 
manufacturer and the employee both feel 
that the recommendations are for their 

* Trans. Ilium. Eng. Soc, U.S.A.. Nov., 

benefit, and are not to be considered as 
a burden. 

Recommendations on the lighting of 
interiors were also recently framed by the 
German Illuminating Engineering Society. 
In scope and principle these also are in 
good accord with those followed in this 

Future Lines of Investigation. 

Statutory regulations on industrial 
lighting should be supplemented by 
unofficial action by societies such as ours, 
which can devote themselves to empha- 
sising the economic as well as the hygienic 
aspects of industrial lighting. Many 
bodies could render valuable aid, and the 
British Industrial Safety First Association 
is already doing so. The American 
I.E.S. Code is revised by a joint com- 
mittee in which the chief engineering 
bodies, Government Departments, etc., 
participate, and a leading part is taken 
by the American Engineering Standards 

Detailed information on the best 
methods of lighting for various industrial 
processes are best arrived at by conference 
and research with representatives of the 
industries concerned, in which both 
employers and employees should take 
part. A precedent in this direction is 
set by the valuable work of the Industrial 
Fatigue Research Board, whose second 
annual report contains a section empha- 
sising the influence of good illumination 
on output, as illustrated by researches in 
the silk industry. The writer would like 
to take the opportunity of referring to the 
valuable work of Mr. D. R. Wilson on 
behalf of the Board, and it is to be hoped 
that before long an improvement in 
economic conditions will render possible 
the fuller encouragement and extension 
of its useful work. Although, up to 
the present, circumstances have prevented 
more than a small proportion of this 
work being devoted to lighting problems, 
enough has been done to show that 
further investigations in this field would 
be well repaid. 

It is also of interest to mention the 
appointment, by the Medical Research 
Council, of a committee to advise them 
on the promotion of researches into the 
biological action of light, with a view 
to obtaining better knowledge of the 



Figs. 6 and 7. — Two views of a clothing factory lighted by gasfilled electric lamps in 
Benjamin reflectors mounted high up near t lie girders and allowing a free view of the 
entire room. A feature of the installation is that no filaments of lamps are visible to an 
observer looking across the room. 



action of sunlight and other forms of 
light upon the human body. Of this 
Committee Prof. W. M. Bayliss, one of 
our members of Council, is the Chairman. 
It would be gratifying if the Committee 
could include in its scope the effect of 
light on the eye, and the study of the 
part played by unsatisfactory lighting 
conditions in causing industrial fatigue. 

International Procedure m regard to 
Industrial Lighting. 
Industrial lighting is now receiving 
attention in various countries, and inter- 
change of views is most desirable, in 
order that any recommendations may 

be based on commonly accepted general 
principles. A useful step in this direction 
was taken by the appointment, at the 
first technical session of the International 
Illumination Commission last year, of an 
international technical committee to 
review the whole subject. Ultimately it 
is to be hoped that an " International 
Code " on industrial lighting may be 
framed. It is also of interest to mention 
that this question is receiving attention 
from the Section of Industrial Hygiene 
of the International Labour Office estab- 
lished by the League of Nations at 
Geneva. Prof. L. Carrozzi. a valued 
member of the Society, is associated with 
this work. 


Mr. D. R. Wilson (Secretary to the 
Industrial Fatigue Research Board) con- 
gratulated Mr. Gaster on the wide field 
covered in his paper. Since he had to 
leave the meeting almost immediately, 
his remarks would be confined mainly 
to the work of the Home Office Com- 
mittee, of which he, in common with 
Mr. Gaster, was a member. He wished 
to refer first to the second interim 
report, lately published, which, although 
small in volume, as compared with the 
first report, contained recommendations 
of a far-reaching and important character. 
He suggested that members of the Society 
should, in the discussion to follow, ex- 
press their views on the recommendations 
made, or notify them either to the Home 
Office or the Committee, as soon as pos- 
sible, without waiting until the question 
of giving statutory force to the re- 
commendations came under consideration. 
As regards the latest work of the Com- 
mittee — the formulation of the actual 
illumination adequate for various kinds 
of work — a report on this fundamental 
question was now in preparation. It 
seemed to him that there was room for 
a great deal more research on this problem 
(particularly on the subjective side) before 
definite legal standards could be laid 
down. For a conclusive study of the 
problem physiological and psychological 
research with a view to finding the ideal 
illumination for different types of pro- 
cesses seemed necessary. This research 
should be supplemented by an exami- 

nation of present-day practice, in order 

to ascertain how far ideal requirements 
were being actually attained. No doubt 
such investigations might occupy several 
years, but he thought that in this matter 
it was better to proceed cautiously so 
that ultimately any standards laid down 
shoukl have a thoroughly scientific and 
authoritative basis. 

The Committee that he represented was 
a small centralised body, and at the 
moment considerations of economy pre- 
vented extension of its work. It was 
obvious that a series of researches such 
as he had indicated would involve heavy 
expenditure if interpreted so as to cover 
the whole field of industries. It had 
been clearly shown that good illumination 
was necessary both to efficiency and 
safety, and the specification of the con- 
ditions of adequate lighting was therefore 
a matter of direct interest to the industries 
concerned. It affected employers and 
workers alike. It appeared reasonable 
therefore that industries themselves should 
be induced to take an active share in the 
collection of the necessary data. Many 
industries had already Research Associ- 
ations or Joint Industrial Councils, and 
while the fundamental study should be 
left in the hands of a central body such 
as the Home Office Committee on 
Factory Lighting, he suggested that the 
various industries, through their own 
organisations, might undertake the 
collection of the data required for indica- 
ting existing practice. He noticed that 



Mr. Gaster had shown a chart indicating 
that the cost of lighting formed only 
0*3 per cent, of the costs of production. 
No doubt in many industries this would 
apply, but in other cases, e.g., the silk 
industry, he believed that the cost of 
lighting formed a more considerable 
proportion. He mentioned this merely 
to show that each industry needed to be 
separately considered and that, without 
studying the conditions in a particular 
case, one could not apply general formula?. 

Mr. J. Herbert Fisher (President of 
the Ophthalmological Society) expressed 
his pleasure at attending the meeting. 
The discussion was of great interest to 
ophthalmic surgeons who had only recently 
come to recognise how many were the 
problems in connection with illumination 
that needed study at their hands. He 
might mention, as one instance of co- 
operation between ophthalmic surgeons 
and lighting experts, the illumination 
of charts used in testing vision, on which 
they had recently come to a useful 
decision, largely through the assistance 
they had received from Mr. Gaster. 
Attention had been drawn to the import- 
ance of good industrial lighting with a 
view to increasing production, and safe- 
guarding the health and vision of workers. 
In this latter connection one important 
consideration to be borne in mind was 
the great variation in the eyesight of 
different workers, especially when there 
was a wide range in their age and fitness. 
Conditions of lighting that would not be 
detrimental to a man of 25 might prove 
quite inadequate for one of 45 or 50, 
whose eyesight would probably be less 
acute. It occurred to him that this was 
one aspect of the problem which might 
well receive attention from ophthalmolo- 
gists, who might undertake the exam- 
ination of the eyesight of the workers 
conjointly with tests of the illumination 
found necessary in different branches 
of industry. 

Mr. W. R. Rawlings said that he was 
attracted by Mr, Gaster's remarks on the 
subject of standardisation of the reflector 
and holder and their position with 
respect to the lamp filament. Possibly 
the British Engineering Standards 
Association could help in bringing about 
such standardisation. It frequently 

happened that a well-designed instal- 
lation was spoiled by the haphazard 
replacement of lamps, with the result 
that they often projected from the 
reflector, giving rise to glare and entirely 
altering the distribution of light. He 
also thought that we were perhaps a 
little in advance of the ordinary consumer 
in the use of technical terms. No doubt 
recommendations should be framed in 
a scientific way, but they should be 
supplemented by simple terms which 
the public could understand. Although 
it was true that such terms as candle- 
power, foot-candles, etc., had become 
much more familiar since the Society 
commenced its work, there were still a 
great many people who did not understand 
them. It had been suggested that com- 
mercial standard be employed such as 
writing, reading or dining-table illumi- 
nation. Such terms could not, of 
course, replace accurate phraseology, 
but he thought they might prove a 
useful addition for the benefit of the 
general public. 

Mr. J. W. T. Walsh {Joint Secretary 
of the Home Office Departmental Com- 
mittee on Lighting in Factories and 
Workshops) congratulated the author 
on the skill with which he had con- 
densed such a variety of information 
and the wide scope he had covered 
in the paper, in comparatively little 
space. He fully agreed with the remarks 
that Mr. Gaster and Mr. Wilson had 
made regarding the enormous amount 
of research work necessary before making 
definite regulations on adequate working 
illumination. Mr. Gaster, he might 
mention, was the British representative 
on the International Technical Committee 
appointed to deal with industrial illumi- 
nation. He felt sure that the time 
required in collecting information and 
making researches would be much cur- 
tailed if the co-operation of workers in 
other countries could be enlisted. There 
was a considerable amount of scattered 
information available if our resources 
in this respect could be ' pooled." He 
hoped that members of the Society 
would keep the National Illumination 
Committee informed of any data and 
information they obtained on this subject. 
No doubt Mr. Gaster would be glad to 



receive and pass on to the Committee such 
information. The problem was such 
an extensive one that supplementary 
assistance of this kind was very useful, 
anrl progress would naturally not be so 
rapid if all the work was left to the 
members of the Committee. Meanwhile 
it was gratifying to recognise that this 
country had taken such a large share 
of the work so far done in the field of 
industrial lighting. 

Mr. P. J. Waldbam expressed his 
interest in the American codes of indus- 
trial lighting. In many respects these 
wen- admirable, but he was struck by the 
high values of illumination recommended 
for industrial Bervice. He thought that 
a systematic comparison of these with 
data acquired by the Home Office 
Committee would yield useful results. 

There may be special reasons (climatic 
or otherwise) to account for the use of 
higher .standards abroad. It appeared 
that two or three foot-candles were there 
regarded as a minimum. He (Mr. 
Waldram) had had occasion to test the 
lighting in a considerable number of 
offices and the proportion of cases in 
which illuminations below two foot-candles 
weiv recorded was very great: the 
number of people who professed to be 
able to work quite well by such an 
illumination was also considerable. The 
amount of work carried out by the Home 
Office Committee and tabulated in its 
reports was enormous and they would 
well repay careful study. He was partic- 
ularly interested in the data given relating 
to daylight illumination. It should be 
possible to form a fairly correct ratio 
relating the illumination in a room to 
the area of sky visible, or the total 
unrestricted illumination out of doors. 
If the Home Office Committee would 
deduce from their data a factor of this 
kind, it would be a most useful guide to 
the design of window-space in factories. 
The need for periodical cleaning of 
windows had also been mentioned and 
he hoped that the Society would use its 
influence in this direction. Few people 
realised the great waste of light that was 
occasioned by dirty windows. By tests 
with a lumeter on a few square inches 
of window, clean and dirty, it would be 
found that a loss of light of 30-40 per 

cent, through dirt was quite common, 
while even 50 per cent, loss might be 
caused by absorption in the case of 
windows that did not appear to the eye 
excessively dirty. It had been stated 
that the cost of good artificial lighting 
formed only a small proportion of 
the costs of production. Nevertheless 
managers were apt to scrutinise this 
item very closely. The amount of day- 
light to be saved by the simple expedient 
of cleaning windows was a point that 
should appeal to managers. It might 
also be mentioned that at present there 
was a great deal of variation to be met 
with in window glass. The loss of light 
through certain varieties was appreciable. 
Finally he hoped that an effort would 
lie mad'' tn impress on managers of fac- 
tories the importance of experiment in 
lighting matters. A certain amount of 
highly useful research could be carried 
out by the actual users of artificial light 
and their experience would be most 
valuable. He was therefore very glad 
to note from Mr. Wilson's remarks that 
the Home Office Committee had in view 
the co-operation of manufacturers in this 

.Mr. J. G. CLARK remarked that, looking 
back over the last eight or ten yen-. 
there had been substantia] improvements 
in the lighting of factories and workshops. 
However, much remained to be done and 
there were great opportunities in this 
field. The manager of a factory naturally 
looked at the problem from a strictly 
economic standpoint, and it was a great 
advantage, from his point of view, if 
improvements could be effected without 
increasing the cost of the energy con- 
sumption. In many factories there was 
undoubtedly a great waste of light and 
it was often possible to improve the 
lighting and yet diminish the cost. 

Mr. Clark also referred to the re- 
commendations contained in the paper 
relating to avoidance of glare. He 
thought that the exact interpretation 
of the clause in the second interim report 
of the Home Office Committee on this 
point was somewhat ambiguous, and he 
would like to suggest that the Committee 
should make some slight modifications 
whereby its meaning could be made 
quite clear and undue glare avoided. 



Capt. E. Stroud wished to draw 
attention to the very important and 
gratifying recommendation which has 
been made by the Departmental Com- 
mittee, in the second report of the 
Departmental Committee on Lighting 
of Factories and Workshops, leading 
to the specifying of a "' cut-off " for all 
reflectors of not less than 20 degrees 
from the horizontal with the centre of 
the lamp filament. 

This recommendation apparently was 
made in the consideration as a preventa- 
tive of glare, but it seemed to him to have 
a still greater importance on the question 
of distribution. It was well known that 
the major portion of the light flux was 
given out from the lamp in the mid-zone 
area. Therefore if this recommendation 
was carried out it would mean that the 
units would give a much more concen- 
trating distribution of light than is the 
case when a flat type reflector is used. 
Flat type reflectors were of little value 
from the point of view of distribution, 
and should never be used in serious 
illuminating problems. The very fact 
that they did not cover the light sources 
precluded the possibility of redirecting 
the light where it was needed, the working 
area, and the major portion of the light 
was dissipated high up round the room, 
causing glare and inefficient illumination 
values. Now, if reflectors were used as 
recommended, the fact that a more 
concentrating distribution would be ob- 
tained would mean that to illuminate 
the whole working area the units would 
have to be placed higher than hitherto 
or they must be closer together. 

With the present high efficiency lamps, 
the natural tendency is higher units 
rather than closer together, which means 
fewer points, less glare and more efficient 
lighting. This was very good modern 
practice and a step in the right direc- 

Now they came to the question of 
glare. Glare as usually understood was 
simply contrast, and while one 1 
opaque reflectors of a comparatively sma 
illuminated area, one must have glare. 
This was due to the small illumina' 
areas contrasting against the dark ceiling 
owing to the opaque reflectors not allow- 
ing any upward light to illuminate the 
upper part of the shop. 

He would like to suggest a more general 
use of translucent type of reflectors 
such as prismatic or opalescent ; these 
reflectors allow a proportion of the light 
to be transmitted in the upward direction 
and reduced the glare effect enormously. 
Workshops lit by this method were 
much more cheerful and the efficiency of 
illumination on the working area was 
greater with the use of translucent 
reflectors of the correct distribution than 
opaque reflectors in a similar situation. 
Furthermore, it seemed possible that 
under conditions of great contrast the 
value of 5 candles per square inch, given 
in the report for the intrinsic brilliancy 
of lighting units, might be glaring, whereas 
if the background were light no glare 
wou'd be noticeable. 

It was obvious from the diagram shown 
by Mr. Gaster that the question of main- 
tenance was a very important one. Too 
much stress could not be laid on the 
importance of maintenance. No matter 
how carefully an installation was worked 
out, how scientifically designed, if such 
installation were not maintained it would 
depreciate and be quite inadequate in a 
very short time. 

Mr. S. B. Chandler said he was sure 
that they had all listened to Mr. Gaster's 
paper with great interest, and he thought 
that the Society was to be congratulated 
on the progress that had been made in 
industrial lighting, largely through its 
efforts. He was glad to observe that 
Mr. Gaster had laid stress on the import- 
ance of careful initial installation of 
lights and maintenance in order to ensure 
that the original standard of lighting 
did not depreciate. In his experience 
the provision of regular and effective 
maintenance was of vital importance, 
in factory lighting. 

Mr. A. Cuxnington (communicated) : — 
In listening to the discussion following 
Mr. Gaster's paper, I was interested to 
note Dr. Fisher's reference to the great 
differences which exist between the eyes 
of one person and those of another. 
This confirms an impression that I have 
obtained through, having to deal with 
a number of cases of alleged defective 
lighting. On investigating we often find 
that what is quite satisfactory for one 



man is not sufficient for another. I 
recollect a case in which a signal box was 
worked by three men each taking a 
shift. Two out of the three were quite 
satisfied with the lighting but the third 
always complained when on night shift. 
It may be argued that if you satisfy the 
person who needs most light, the others 
will not mind having more than they 
require. But is this efficient Lighting ? 

And that suggests another point which 
I should like to emphasise, viz., that the 
tendency for standards of illumination 
to be raised may be carried too far. It 
is common knowledge that, speaking 
generally, every improvement in efficiency 
of light sources has in the |>ast been 
used to give more light at the same cost 
rather than the same Ight at less cost. 
The result has been that standards of 
illumination have leapt up during the 
last few years, and this is especially 
noticeable in the United States. ( )ur 
eyes get so accustomed to hij:li intensities 
that after a while we cannot do without 
them. I have been looking over records 
of illumination taken during the last ten 
years. I find that ten years ago two 
foot-candles was considered an adequate 
minimum for a desk. Now three foot- 
candles is the figure put down in " codes," 
and possibly in another ten years no one 
will be content with less than five foot- 

These reflections force one to the con- 
clusion that, in legislating, an uppei limit 
will be required as well as a minimum. 
Otherwise what is to prevent a factory 
owner, influenced by someone selling 
high candle-power lamps, from providing 
an intensity of illumination so great that 
if any of his workpeople were transferred 
to a factory with ordinary lighting they 
would at once protest that they could 
not see. I have com across many cases 
in which clerks have been transferred 
from an over-lighted desk to one with 
normal but adequate illumination, when 
they have made strong complaint. 
Their eyes had been spoilt for ordinary 
lighting. It appears that the need for 
dealing with wide diversity in the per- 
sonal factor and protection from over- 
lighting will best be met by prescribing 
for each class of work upper and lower 
limits of illumination, with a fairly 
wide margin between. 

Mr. W. A. Bishop (comm u n icated) : — The 
views expr ssed by our esteemed Hon- 
orary Secretary are of special interest as 
coming from one familiar with inter- 
national developments. It occurs to me 
that a few words on industrial lighting 
from the standpiont of gas engineers may 
be of service. Neither gas nor electric 
lighting can have a monopoly, but indus- 
trial lighting is of special importance as 
a field for gas, in view of the oppor- 
tunities presented for heating as well as 

In the paper read before the Society 
on December 13th, a review of progress in 
gas lighting was given, and some refer- 
ence was then made to factory lighting. 
I may mention that in my own town the 
illumination provided on actual benches 
and machines is usually from 4 to 6'5 
foot-candles. It is our practice to supple- 
ment local working illumination by 
overhead lights, giving a general illumin- 
ation of 0*5 foot-candles. The lamps 
illustrated in the slides, shown by Mr. 
Gaster, of a gas-lighted iron works at 
Croydon, form part of an installation of 
twenty-nine 1,500 and 1,000 candle- 
power lamps operating at 81 in. pressure. 
The interior of the workshop is white- 
washed and the lamps are spaced 24-30 ft. 
apart and 25 ft. above floor-level. This 
general lighting is reinforced by portable 
" spot " electric lighting, plugs being 
arranged round the workshop. The 
mean illumination provided by this 
system of gas lighting is 3-4 foot-candles. 
Another installation of interest is that in 
a constructional engineering workshop 
using twenty-one 150 candlepower lamps 
and thirty-five lamps of 300 candle- 
power (nominal). The burners each 
consume about .1*3 therms per hour, 
costing, at Is. Id. per therm, Is. 5d., and 
the maintenance costs, including labour 
charges, also Is. 5d. per burner per annum. 
The actual mantle renewals per burner 
per annum were 1*02 for the year ending 
December, 1921 ; 33 per cent, of the total 
maintenance charge relates to labour. 

With regard to the screening of light- 
sources, although the intrinsic brilliancy 
of gas-lighting is relatively low, the 
brightness of mantles needs to be dimin- 
ished when they are placed within the 
direct range of vision. This can be 
readily effected by the use of vitreosil 



glassware, which conforms with the 
requirement laid down in the Home 
Office Departmental Committee's report, 
namely, that no light-sources shall be 
directly visible to the eye. My experi- 
ence is generally in accordance with that 
of Mr. J. G. Clark, who mentioned in the 
discussion last December that vitreosil 
reduces the brightness of mantles to about 
10 candles per square inch. I should be 
interested to hear, however, if any experi- 
ments have been made on the possible 
alteration in quality of light by this 
material, e.g., whether it leads to any 
appreciable increase in the ultra-violet 
component. As regards local lighting 
screening is readily effected by using 
deep reflectors, while for general lighting 
Messrs. Keith and Blackman have intro- 
duced a circular opal band having a depth 
equivalent to the length of the mantle. 
In the case of a 500 candlepower lamp 
with clear globe this opal screen would 
only reduce the mean lower hemi- 
spherical candlepower by about 9 per 

So far I have dealt mainly with high- 
pressure gas lighting. In the paper last 
December reference was made to the 
good effects obtained with small mantle 
clusters on low pressure superheated 
burners, yielding about 64 candle-hours 
per centi-therm. We have just equipped 
a large distillery on the outskirts of 
Croydon with a number of these lamps 
in three, four, six and eight burners sizes. 
Installation costs are lower and main- 
tenance expenses very favourable with 
this system, which should prove of in- 
creasing importance. The durability of 
the small mantle is well recognised, and 
I feel sure that it has come to stay. I 
may mention that one six-burner cluster 
with a fairly steep enamelled reflector, on 
gas of a little under 500 B.Th.U.per cubic 
foot, and with 25/10 pressure, yielded 
on test the remarkably high value of 
50 candles per cubic foot per hour 
(mean of eight equi-distant angular read- 
ings), and gave just under 1,000 candles 
at 60°. 

. In conclusion, I think there is need for 
co-operation among gas lamp manu- 
facturers in standardising reflectors, | 
ticularly for workshops. I should also 
like to emphasise the importance 
paying careful attention to the installation 

and running costs of the two methods of 
gas lighting referred to. I regard with 
respect the activities of my electrical 
colleagues who. in a general manner, have 
given the gas men a lead in the science 
of illumination, and must say that it was 
an electrical member of this Society who 
put me on the right track in regard to the 
study of these problems, and introduced 
me to the Society, where for a brief 
period of our lives both gas and electrical 
men cut out commercial rivalry and 
pool the available brains in the cause of 

Mr. Leon Gaster, in reply, expressed 
appreciation of the manner in which his 
paper had been received. He felt sure 
that all present would approve the 
practical method of procedure proposed 
by Mr. Wilson as a basis of further 
investigations. The chart he (Mr. Gaster) 
had shown illustrating the proportion of 
the total cost of production formed by 
lighting in a machine shop was based on 
pre-war figures. Naturally the ratio 
varied in different industries, but the 
cost of efficient lighting was small in com- 
parison with the benefits received. Mr. 
Wilson had invited comment on the 
Home Office Committee's report and he 
was glad to note that some useful sugges- 
tions had been made. He entirely agreed 
with Mr. Herbert Fisher as to the impor- 
tance of examination of the eyesight of 
workers. The latter should be classified 
according to the demands of the industries 
on the eyesight, and the illumination 
available. The suggestion of Mr. Raw- 
lings, that simple methods of conveying 
values of illumination should be devised 
for the benefit of those who did not 
understand the " foot-candle " was a 
o;ood one. He hoped, however, that this 
term, already much more familiar than 
a few years ago, would eventually become 
as well understood as " candlepower." 
Mr. Cunnington had urged that economy 
should not be overlooked in fixing stan- 
dards, and excessive illumination avoided. 
Judicious economy was naturally desir- 
able, successful illuminating engineering 
should eliminate extravagance, and 
proper standards would doubtless operate 
not only in raising the level of illumin- 
ation where inadequate, but in showing 
where an unnecessary amount of light was 



being used. But it appeared probable 
that in most eases the illumination pre- 
vailing in factories was too low, rather 
than excessive. Finally, he appreciated 
Mi. Bishop's summary of developments 

in industrial lighting with gas, and 
especially his acknowledgment of the 
services of the Society in affording useful 
information to both gas and electrical 



(Proceedings at the joint meeting of the Illuminating Engineering Society and the Royal Aero- 
nautical Society held at the House of the Royal Society of Arts, 18, John Street, Adelphi, 
London, W.C., at 8 p.m., on Tuesday, January 31st, 1922.) 

(Continued from //. 63 in February issu 

Lt.-Col. L. F. Blaxdy, D.S.O. {in 
reply to the discussion) : I observe that 
most of the points raised in the discussion 
have been dealt with by other speakers. 
Colonel O'Corman referred to the danger 
of fire from electrical causes and to the 
question of weight in the design of 
navigating lights. Exhaustive investi- 
gations, extending over a period of 
years have taken place with a view to 
determining the causes of fire in aircraft. 
The results go to prove — as far as such 
a point can be proved — that no fire has 
ever been due to the breaking of a low 
tension electric circuit, such as is used 
for lighting purposes. The elimination 
of every ounce of unnecessary weight has 
received prime consideration in design- 
ing navigation lights. The latest lighting 
systems are very much lighter than those 
in use during the war, but it must be 
recognised that the reliability and effi- 
ciency of these lights is of the highest 

Lt.-Col. Silvester Evans refers to the 
use of 24 in. projectors for illuminating 
a landing ground. It will be of interest 
to him to know that recent night flying 
has demonstrated the great efficiency of 
the 36 in. beams, having a dispersion of 
45°, used at Croydon for this purpose, 
and that the Air Ministry will shortly be 

in a position to try 24 in. beams. Com- 
parative tests of the 36 in. and 24 in. 
will show whether the latter gives suffi- 
ciently good results. 

.Major Ashley Waller has made some 
interesting remarks, and in reply I would 
like to say that the lighting of existing 
aerodomes from a central point has been 
considered, but as this would involve the 
erection of further obstructions it has 
not found favour with the pilots using 
these aerodromes. Furthermore, this 
scheme entails throwing light directly 
into the face of the pilot landing, which 
is undesirable. 

The sun-valve control is for various 
reasons considered more suitable than 
any clockwork mechanism ; the use of 
the latter necessitates a train of gear 
wheels, also some form of spring liable 
to changes in tension under varying 
temperatures. In addition, clockwork 
mechanism needs frequent adjustment 
in latitudes where the hours of daylight 
are subject to marked variation. Further- 
more, cases have occurred where pilots 
have been able to locate an aerodrome 
during mist and rain by means of a sun- 
valve controlled lighthouse working at 
an hour when clockwork would have 
been inoperative. 




(Held at the Trocadero Restaurant, Piccadilly, London, W.C., at 7.30 p.m., en Friday, 

February 10th, 1922.) 

The Annual Dinner of the Illuminating 
Engineering Society was held at the 
Trocadero Restaurant at 7.30 p.m. on 
Friday, February 10th, the President 
(Sir John Herbert Parsons, C.B.E., 
F.R.S.) being in the Chair. There was 
a representative assembly of members 
and guests, among whom the following 
may be mentioned : Sir Herbert Jackson, 
K.B.E., F.R.S. (the Royal Society) ; 
Maj.-Gen. Sir Frederick Sykes, G.B.E., 
K.C.B., C.M.G. (Controller-General of 
Civil Aviation) ; the Right Hon. William 
Brace, P.C. (Mines Department) ; Mr. 
Thos. Hardie (President of the Institution 
of Gas Engineers) ; Mr. A. A. Campbell 
Swinton (Vice-President of the Institu- 
tion of Electrical Engineers and Chairman 
of the Royal Society of Arts) ; Mr. J. B. 
Lawford, F.R.C.S., M.D. (Chairman of 
the Council of British Ophthalmologists) ; 
Mr. J. Herbert Fisher, F.R.C.S., M.B., 
■ B.S. (President of the Ophthalmological 
Society) : Mr. R. E. Graves, C.B.E. 
(H.M. Chief Inspector of Factories) ; 
Mr. H. E. Blain, C.B.E. (Hon. Secretary 
of the British Industrial " Safety First " 
Association) ; Mr. Joseph Orringe (Presi- 
dent of the Electrical Contractors' 
Association) ; Alderman George Clark, 
J. P. (Chairman of the Society of British 
Gas Industries) ; Sir William T. Lister, 
K.C.M.G., M.B., F.R.C.S. ; and Mr. W. T. 
Holmes Spicer, F.R.C.S. A full list 
of those who were present will be found 
on p. 90. Among those who wrote 
expressing regret at being unavoidably 
prevented from being present were : 
Professor Sir Charles Sherrington (Presi- 
dent of the Royal Society) ; Sir Frank- 
Heath (Director of the Department for 
Scientific and Industrial Research) ; and 
Sir Thomas Oliver. 

Toast . " The Illuminating Engineering 
Society. " 

After the usual loyal toasts had been 
honoured the toast of " The Illuminating 
Engineering Society " was proposed by 

Sir Herbert Jackson, K.B.E., F.R.S. 
{the Royal Society), and seconded by Mr. 
J. B. Lawford, F.R.C.S., M.D. {Chair- 
man of the Council of British Ophthalmo- 
logists). The toast was coupled with 
the name of the President (Sir John 
Herbert Parsons, C.B.E., F.R.S.). 

Sir Herbert Jackson said that he 
had watched with great interest the 
work of the Society, and had been 
much impressed by the variety of its 
activities. He recalled that many years 
ago he was associated with the Hon. 
Secretary, Mr. L. Gaster, in some 
researches on chemically-treated carbons 
— a method which was developed a 
considerable time afterwards in the flame 
arc lamp. In addition to its study 
of lamps and lighting appliances the 
Society had paid special attention to the 
effect of light upon the eye, and it was, 
therefore, fitting that in the person of 
their President ophthalmic science should 
be represented. He recalled that one 
of the very earliest discussions, initiated 
at a meeting of the Society by the 
President, related to the causes and 
effects of glare. Since that date new 
and brighter illuminants had been 
developed, and there was still ample 
scope for the Society's influence in 
this field. The avoidance of glare was 
bound up with the problem of designing- 
suitable shades and reflectors, and he 
understood that the Society had done a 
great deal towards encouraging their 
use. In associating the toast with the 
name of the President, he wished to 
congratulate him on tin' receipt of his 
well-merited knighthood. He believed 
that this was the first occasion, since this 
honour was conferred, that Sir John 
Herbert Parsons had presided over a 
public gathering. 

Mr. J. B. Lawford. who also offered 
hia congratulations, stated that the 
Council of British Ophthalmologists had 

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been associated with the Illuminating 
Engineering Society in the study of 

various problems, and it was now well 
recognised that there were many oppor- 
tunities for joint action by lighting 
experts and ophthalmic surgeons in con- 
nection with the application of artificial 
light. This followed as a natural con- 
sequence from the fact that the ultimate 
judge of what constituted good illumina- 
tion was the human eye ; everything 
possible, therefore, should be done to 
provide lighting conditions which, besides 
being efficient, contributed to comfortable 
vision. The President had taken the 
lead in encouraging the study of illumina- 
tion by ophthalmologists and there was 
no doubt that the Society had already 
achieved a great deal of useful work. 
He hoped that in the future there would 
be further opportunities for fruitful 
co-operation between members of tin- 
Society and ophthalmic surgeons. He 
had accordingly much pleasure in second- 
ing the toast of ' : The Illuminating- 
Engineering Society " coupled with the 
name of Sir John Herbert Parsons. 

The President (Sir John H. Parsons), 
in replying to the toast, reviewed the 
progress of the Society since its inception 
in 1919, when he formed one of the 
original members. A feature of the 
Society's work from the very first had 
been the way in which it led them into 
co-operation with other bodies. Quite 
early in their history they had formed 
joint committees to deal with such 
subjects as the fighting of schools, 
libraries, streets, etc., and they had 
followed the same course more recently 
in various investigations connected with 
the cinema industry. His own experience 
as a member of the Home Office Depart- 
mental Committee on Lighting in Fac- 
tories and Workshops had shown how 
much there was to be done in the field of 
industrial lighting. Sir Herbert Jackson 
had referred to their early studies of 
glare. This was a problem that they had 
recently had to consider in connection 
with factory lighting ; in fact, the pro- 
vision of sufficient illumination, and the 
avoidance of glare formed the basis of a 
very large number of lighting problems. 
He felt sure that ophthalmologists would 
be only too glad to help in the solution 

of such problems. He thanked the 
proposers of the toast for the kind terms 
in which they had referred to his services, 
but he wished to point out that the 
success of the Society was very largely 
due to the efforts of their Hon. Secretary. 
Mr. L. Gaster, who has shown such 
fertility of resource in bringing together 
all those interested in various aspects 
of illumination. 


Kindred Societies." 

Mr. F. W. Goodexough (Vice-Presi- 
dent), in proposing the toast of " Kin- 
dred Societies," remarked that previous 
speakers had already referred to the 
great variety of societies and associations 
who had shared with the Illuminating 
Engineering Society the task of promoting 
a better knowledge of the essentials of 
good illumination. Many of these bodies 
were represented at the dinner, and it 
gave him great pleasure to couple the 
toast with the names of Mr. Thomas 
Hardie (President of the Institution of 
Gas Engineers) and Mr. A. A. Campbell 
Swinton, who was present in a dual 
capacity — as a Vice-President of the 
Institution of Electrical Engineers and 
as Chairman of the Royal Society of Arts. 

One of the most pleasant features of 
the Society's work was the opportunity 
it provided for gas and electrical engineers 
to meet on a common impartial platform 
and discuss topics of mutual interest, 
and he felt sure that those associated 
with both illuminants had learned a great 
deal from such discussions. It was now 
admitted that there were principles 
common to all methods of lighting that 
provided a useful field for research, and 
that representatives of all systems of 
illumination could unite their efforts in 
endeavouring to bring about a better 
appreciation of the value of good lighting. 
They were also glad to have the oppor- 
tunity of welcoming Alderman Clark, 
the Chairman of the Society of British 
Gas Industries, and Mr. Joseph Orringe, 
President of the Electrical Contractors' 
Association. The equipment and upkeep 
of lighting installations rested very 
largely in the hands of contractors, and 
it was of great importance that they 
should study the work of the Society. 
The maintenance of lighting installations 



was quite as vital as the adoption of 
correct methods when it was originally 
designed and the leading gas companies 
attached great importance to providing 
services of this kind. 

Lastly, he wished to refer to another 
body, which, like the Illuminating En- 
gineering Society, had been concerned 
with all illuminants — the Royal Society 
of Arts, whose hospitality the Society 
had enjoyed from its inception. The 
Royal Society of Arts had, in the past, 
been quick to record each development 
in illumination as it occurred, but had 
subsequently resigned to the Illuminating 
Engineering Society the task of dealing 
with all aspects of illumination, receiving, 
however, from its Hon. Secretary (Mr. 
Gaster) periodical papers, furnishing a 
record of progress. He had much pleasure 
in proposing the toast of " Kindred 
Societies " coupled with the names of 
Mr. Thomas Hardie and Mr. A. A. 
Campbell Swinton. 

Mr. Thomas Hardie [President of 

the Institution of Gas Engineers), ex- 
pressed his pleasure in attending the 
dinner and fully concurred in Mr. Good- 
enough's remarks on the subject of 
co-operation between engineers associated 
with both gas and electric lighting. 
Although rivals in many fields, representa- 
tives of both illuminants had come to 
realise how wide was the field for common 
action, particularly in educating con- 
sumers in the proper use of light. The 
Illuminating Engineering Society had 
done and was doing excellent work 
which was appreciated by the gas in- 
dustry. Within recent years there had 
been many suggestions as to how gas 
and electric supply undertakings could 
co-operate, and it seemed probable that 
in the future these proposals would take 
more definite shape and would further 
facilitate the useful work on which 
the Illuminating Engineering Society 
was engaged. 

Mr. A. A. Campbell Swinton, F.R.S. 
(Vice-President of the Institution of Elec- 
trical Engineers and Chairman of the 
Royal Society of Arts), briefly acknow- 
ledged Mr. Goodenough's kind references 
to the two bodies which he represented. 
He entirely agreed with the remarks of 

both Mr. Goodenough and Mr. Hardie 
regarding co-operation between those 
icsponsible for gas and electric supply 
undertakings. During recent vears there 
had been a considerable change in 
outlook in this respect, and he, personally, 
saw no reason why such bodies should 
not work together much more closely 
in the future than in the past. He 
himself had been associated with some 
of the earliest developments in electric- 
lighting, and had watched the industry 
develop from its early stages. The 
progress during recent years, both in 
the efficiency of illuminants and in the 
knowledge how to make the best use of 
them, had been remarkable, and there 
was no doubt that the existence of the 
Illuminating Engineering Society had 
done a greal deal to foster developments 
and disseminate knowledge of illu- 
mination. The work of the Society 
had many ramifications, and there was 
never a better field for its activities 
than at the present time, when so many 
varieties of lamps and fittings were 
available to the consumer. He wished 
the Society continued success and a 
prosperous future. 

.Air. Goodenough had referred to the 
fact that meetings of the Society were 
held in the House of the Royal Society 
of Arts. Some of those present were 
aware that the Royal Society of Arts 
had purchased the building and hoped 
to redecorate it shortly, when no doubt 
the lighting, heating, and ventilating 
would be rearranged on the most modern 
lines, so that the Illuminating Engineering 
Society would hold its meetings under 
comfortable conditions. It was true, as 
Mr. Goodenough had said, that the 
Royal Society of Arts had been re- 
sponsible for the launching of many 
new ideas, and had encouraged the forma- 
tion of many of the younger societies, 
and he hoped that they would meet 
with generous support towards the im- 
provement of their home. 

Toast : " The Guests.'' 

Mr. L. Gaster (Hon. Secretary) in 
proposing the toast of " The Guests," 
remarked that the Society had always 
had a cordial and sympathetic hearing, 
when approaching Government Depart- 
ments or other bodies with requests for 



co-operation. This was due to the fact 
that before taking steps in such cases 
they formed a clear conception of what 
was needed, and waited until the ground 
was prepared so that they had a good 
case to present. Although it was only 
possible to associate with the toast the 
names of a few of the distinguished 
guests present, he hoped that his remarks 
would be interpreted as expressing a 
cordial welcome to all. 

The first name on the list was that of 
the Right Hon. William Brace, P.C., 
of the Mines Department. Lighting 
in mines was of great consequence to the 
worker. The Society had arranged a 
discussion on this subject in 1920, in 
which a large number of eminent oph- 
thalmologists took part. There was a 
consensus of opinion that the disease 
known as " Miners' Nystagmus " was 
directly associated with inadequate illu- 
mination. The valuable work of Dr. 
Llewellyn and others in this country, 
which led to this conclusion, had been 
confirmed by the valuable researches 
of Dr. Stassen in Belgium, whose co- 
operation in this discussion aptly illus- 
trated the value of the Society's inter- 
national relations. He was glad to say 
that the authorities had taken a leading 
part in encouraging experiments on 
miners' lamps, and he wished to assure 
Mr. Brace of the desire of the Society 
to be of any further service in this 

He wished next to welcome Mr. Graves, 
H.M. Chief Inspector of Factories, and to 
express his appreciation of the sympa- 
thetic attitude which the Home Office had 
taken towards industrial lighting. It was 
now quite a number of years since they 
were first in touch with the Home Office 
on this subject, and, as many of those 
present were aware, this country had 
taken the lead by the appointment of the 
Home Office Departmental Committee on 
Factory Lighting, of which both he 
(Mr. Gaster) and the President were 
members. The success attending the 
Society's efforts was due very largely to 
the recognition that in such matters one's 
ideal should be " Government by Con- 
sent " and the Committee had wiseiy 
contented themselves with recommenda- 
tions which could be accepted 
employers and workers alike, as mad- 

their own interests. There was now a 
general recognition that good industrial 
lighting was essential in the interests of 
safety, efficiency and health. 

One of the most important aspects of 
factory lighting was its relation to safety, 
and a direct relation had been established 
between the prevalence of accidents and 
the lighting conditions. He therefore 
gladly took this opportunity of paying 
a tribute to the work of the British 
Industrial " Safety First " Association, 
whose hon. secretary, Mr. H. E. Blain, 
had been such a good friend to the 
Society. The Association had recently 
published and circulated a special leaflet 
endorsing the value of good industrial 
lighting in the interests of safety, and on 
various occasions it had taken steps to 
bring this matter to the notice of manu- 
facturers throughout the country. He 
had no doubt that in the future the co- 
operation of the Society with the British 
Industrial " Safety First " Association 
would have most valuable results. He 
would like to remind those present that 
Mr. Blain, apart from his association with 
this work, had another source of interest 
in illumination through his association 
with the Underground Railways of Lon- 
don, which, as the notices in the buses 
stated, used upwards of 160,000 lamps 
and " lighted their own streets." There 
were many excellent instances of lighting 
on the Underground Railways, and it was 
generally agreed that in the darkened 
London of war times, the tubes, relatively 
brightly lighted as they were, came as 
a great relief. 

He asked members present to drink 
the toast of " Our Guests," coupled with 
the names of Mr. Brace, Mr. Graves and 
Mr. Blain. 

The Rt. Hon. William Brace, in 
replying to the toast, expressed his great 
interest in the work of the Society. He 
himself, in his early years, had worked in 
the mines, and had practical experience 
of the great importance of proper lighting. 
As Mr. Gaster had mentioned, his own 
Department took a keen interest in this 
matter, and many experiments on miners' 
lamps had been made during recent years. 
The surroundings in mines were so dark 
that even a relatively small improvement 
in light was a great relief, and anything 



which the Society could do to encourage 
advances would be most welcome. Refer- 
ence had been made to the relation 
between lighting and miners' nystagmus, 
but there was another aspect, the relation 
of illumination to safety, which was most 
important. It was generally recognised 
that inadequate lighting had proved a 
source of accidents in mines, as had 
already been shown to be the case in 

Mr. R. E. Graves, C.B.E. (H.M. 
Chief Inspector of Factories) expressed his 
appreciation of Mr. Gaster's kind refer- 
ences to his Department, and endorsed 
what had been said regarding the impor- 
tance of good industrial lighting. Members 
of the Society would be familiar with the 
contents of the reports issued by the 
Departmental Committee on Lighting in 
Factories and Workshops. The first 
of those was fully discussed before the 
Society when it appeared, and he under- 
stood that the second report, issued last 
year, would be dealt with in a forth- 
coming discussion before the Society. He 
wished to take this opportunity of acknow- 
ledging the valuable work that the 
Society had done in the field of industrial 
lighting. It was only after the Society 
had approached them on the subject thai 
it had been actively taken up by his 
Department and he appreciated the 
recognition that they had spared no pains 
in dealing with the matter, when the 
necessary expert assistance became avail- 
able. It had been mentioned that the 
President and Mr. Gaster were members 
of the Departmental Committee and their 
help in dealing with these problems had 
been of very great value. 

Mr. H. E. Blaix, C.B.E. (Hon. 
Secretary of the British Industrial " Safety 
First " Association) alluded to the assist- 
ance which the Association had received 
from Mr. Gaster on various committees 
dealing with lighting. Their Association 
was much interested in the relation 
between the prevalence of accidents and 
lighting conditions, and they were now 
endeavouring to obtain further statistics 
of accidents in factories which should 
prove valuable in this connection. There 
were, however, many other fields of 
lighting where the experience of the 
Society had also been most useful, notably 
in connection with street-lighting and its 
influence on traffic. Here again, .Mr. 
Gaster's help had been of great value to 
the London ' ; Safety First " Council, 
whose reports had contained frequent 
references to illumination. Reference 
had been made to the lighting of the 
Underground Railways, and he was glad 
to hear that t he conditions of illumination 
were considered to be good. They had 
taken ;i great deal of trouble with the 
lighting of the tubes and the subject was 
of very greal importance; it was only 
by means of uood lighting that they were 
able to deal safely with the very crowded 
traffic that was met with during rush- 

In conclusion the President proposed 
the health of the Hon. Secretary (Mr. 
Gaster) which was drunk with enthusiasm. 
It was agreed that the evening had been a 
most successful one, and there was a 
general recognition of the value of the 
work that the Society had so far carried 
out and the great scope that existed for 
its activities in the future. 


We have received an intimation of the 
Montefiore Trienniel Prize, the value of 
which is the accumulated interest, for a 
period of three years, from a capital of 
150,000 Belgian francs at .3 per cent. 
The prize is awarded every three years 
as the result of an international com- 
petition for the best original work on 
scientific advances and progress in the 
technical application of electricity. 

The committee is composed of five 
Belgian and five foreign electrical engineers 
under the presidency of the Professor 
of the Montefiore Electrotechnic Institute. 
Whether printed or typed, tw T elve copies 
of the treatises must be submitted before 
April 30th, 1923, to " M. le secretaire- 
archiviste de la Fondation George Monte- 
fiore, a l'hotel de l'Association rue 
Saint-Gilles, 31, Liege (Belgique)," from 
whom further particulars may be obtained. 


INDEX, March, 1922. 


Editorial. By L. Gaster 69 

illuminating Engineering Society— 

(Founded in London, 1909) 

Account of Meeting on February 28th . . . . . . . . . . 73 

Industrial Lighting : Ideal Requirements (Legislative and Otherwise) 

and Practical Solutions. By L. (Faster .. .. .. .. 74 

Discussion : D. K. Wilson (Sec, Industrial Fatigue Research 
Board) — J. Herbert Fisher (President of the Ophthalmologics! 
Society)— W. R. Rawlings— J. W. T. Walsh— P. J. Waldram 
—J. G. Clark— Capt. E. Stroud— S. B. Chandler— A. 
Cunnington — W. A. Bishop — L. Gaster (in reply) . . . . 82 

The Use of Light in Aerial Navigation : Reply to Discussion by Lieut. - 

Col. L. F. Blandy " 88 

Annual Dinner, held on February 10th, 1922 . . . . . . 89 

Mines, Lighting of, in relation to Miners' Nystagmus (Report of the 

Committee under the Medical Research Council) . . . . . . 97 

Topical and Industrial Section . . . . . . . . . . . . 95 


[The contents of these pages, in which is included information supplied by the makers, will, 
it is hoped, serve as a guide to recent commercial developments, and we welcome the receipt of all 
bona-fide information relating thereto.] 

LUMINOUS SIGNALLING APPARATUS, the "Barrow" suspension fittings, and 

A recent list issued by Messrs. Siemens mention is made of a number of recent 

Brothers & Co., Ltd.; on the above installations in which these appliances 

subject deal, with a useful form of were . usecL ™ booklet contains as 

signalling apparatus which will doubtless frontispiece, the familiar view illustrating 

prove useful to power stations, etc., in the U se of central stispension Barrow 

affording a convenient means of com- lighting in Hyderabad, In. ha. 
munication between switchboards or 

control rooms and engine rooms. The OSRAM GASFILLED DAYLIGHT 
equipment comprises a transmitting and LAMPS FOR COLOUR-MATCHING. 

receiving apparatus and a Klaxon horn T . , , , . . , , . ,, 

n . u ° ir i ■ rp, - ,,„ In view of the interest being taken in 

or other calling device, lhe receiver , . ..„ ... ,. ,, 9 , 

,-i- , ■ b •,, , .- , + systems of artificial davhght tor colour- 

utilises a cast-iron case with glass front J , , . ,. • -. . , 

„„,-,,, j i i matching, attention mav be paid to the 

on which orders are conveved ov lummi m- -v-i-r e ■ *• * "i i n \lu 

• i- .■ r^, • ■ , * , possibihtv ot usmg tinted bulbs with gas- 
mdications. The engine attendant can !.,, , , . ,°. , , *>„ 

, l i • i u e - ~ i tilled lamps tor this purpose. A leaflet 

acknowledge signals by means ot a push- . , . \, ~ / „. ^ . „ T , 

u 4.4. v i, ,'.. i • >i issued bv the General Electric Co., Ltd., 

button switch, and the aural signal :11 • . . . . . 

continues until this acknowledgment is U !f at '.' s a colour-matching lamp using 

received. The apparatus thus affords an ^ llbs of , s P ecial , f 1 * 88 developed at the 

• , ,. ■ . ll e ., . ■ • , tompanv s works at Lemington. lhe 
interesting instance ot the combmati >n , ■•JT « , , ? 

e i 4. -ii i . ., lamps are recommended tor use in textile 

ot an appeal to the eve and to the ear. m z\C, i • - • i • * i 

F1 * mills, colour-printing works, picture gal- 

CTDirirT nruTiNr leries and studios, dental and operating 

aiKfcfcl jjiuniiflb. theatres, and other places where correct 

A recent booklet issued by tin' Wai ll< appearance of colours is of importance. 

Engineering Company ("Good Light- An illustrated price list (Xo. O.S. 2706) 

ing") contains some notes on - is obtainable from the General Electric 

lighting and appropriate forms Co., Ltd. (Magnet House. Kingsway, 

lanterns. Special reference is mad London. W.C.2). 




Recent developments in " artificial 
daylight " are illustrated by the Holo- 
phane Daylight Unit, the essential fea- 
tures of which are shown in the ac- 
companying sketch. The unit consists 
of a combination of a Holophane reflector, 
the outer surface of which is protected 
by an aluminium covering and a dish of 
Chance's Daylight Glass, which provides 
the necessary correction to convert the 
light from a gasfilled lamp into a very 
close resemblance to average daylight. 
In view of the fact that about 60 per cent, 
of light may be absorbed in the conver- 
sion in order to imitate daylight ac- 
curately, the correct distribution of the 
light available, with minimum absorption, 

using these colour-matching units, care 
should be taken to screen off any stray 
uncorrected light in the vicinity. 

The unit as a whole has a compact 
and pleasing appearance, features being 
the absence of glare owing to exposure of 
the filament and the special provision for 
ventilation — an important consideration 
in units of this class. It is expected that 
the Holophane Daylight Unit will prove 
useful for the many processes where 
correct appearance of colours is desired, 
e.g., to those concerned with the manu- 
facture and handling of coloured goods 
of all kinds, objects of art, etc., and to 
dyers, colour printers, paper bleachers, 
wool scourers, sugar refiners, millers, 
dentists, medical men, etc. 


' l/en/i/a/ea 

C cmopy 

(Z)ay/'qhf (j/ass 



is of importance. The Holophane re- 
flector employed has been selected with 
a special view to good downward light - 

Three sizes of units, adapted respec- 
tively for use with 100 watt, 150 — 200 
watt, and 300 — 500 watt gasfilled lamps, 
are available, but in view of the relatively 
low intensity of illumination obtained 
with the 100 watt lamps, the larger units 
are recommended where accurate colour- 
matching is to be done. Attention is 
drawn to the desirability of using lamps 
on the right voltage so as to obtain the 
correct colour of light, and of replacing 
lamps before they have appreciably 
deteriorated. It is also important that 
units should be kept clean from dust, 
both inside and outside. Naturally in 


We understand that at the Hilary 
Term Examinations of students of the 
Inns of Court, held at Middle Temple 
Hall on December 12th, 13th, 14th, 
15th and 16th, Mr. George Julius 
Webber, a member of Middle Temple and 
eldest son of Mr. J. Webber (Managing 
Director of the Provincial Incandescent 
Fittings Co., Ltd., more popularly re- 
ferred to by their Trade Mark " Pifco " 
Ltd.), entered for his Bar final examina- 
tion, and out of 134 students lie dis- 
tinguished himself by gaining a first of 
firsts, for which he was awarded a 
Studentship of 100 guineas per annum, 
tenable for three years. 



First Report of the Miners' Nystagmus Committee.* 

Readers will recall that, in a discussion 
on this subject before the Illuminating 
Engineering Society, 1920, f it was 
generally agreed that the disease of the 
eyes known as " miners' nystagmus," 
which has given great concern during 
recent years, was mainly due to inade- 
quate lighting. 

In the same year the Medical Research 
Council appointed a Committee on 
Miners' Nystagmus, the members of 
which are :— Prof. J. S. Haldane, M.D., 
F.R.S. (Chairman), Prof. E. L. Collis, 
M.D., M.R.C.P., Dr. T. L. Llewellyn, 
M.D. (Secretary), Mr. G. H. Pooley, 
F.R.C.S., and Dr. W. H. R. Rivers, M.l).. 
F.R.S. At the request of the Home 
Office, and on the recommendation of 
the Miners' Lamp Committee, the Com- 
mittee has since been engaged in studying 
the causation and means of prevention 
of this disease. The first report of the 
Committee has now been issued, and 
contains an introduction summarising 
its primary conclusions. In addition 
an account of the main part of their 
investigations, together with a report 
of previous researches, is given in special 
reports by Dr. T. Lister Llewellyn and 
Dr. W. H. R. Rivers. 


The Committee have unanimously 
reached the following conclusions : — 

1. The essential factor in the produc- 
tion of Miners' Nystagmus is deficient 
illumination. Other factors, such as 
position during work, accidents, alcoholism, 

* Special report series No. 65. Issued by 
the Medical Research Council, and publis e<l 
by H.M. Stationery Office (Imperial House, 
Kingsway, London, W.C.2), 1922. Is. 6d. net 

t Illum. Eng., March, 1922. 

infections, malnutrition, hereditary pre- 
disposition and errors of refraction, are 
of secondary importance only, while depth 
of workings, thickness of seams and the 
ordinary gaseous impurities in mine air 
have no direct influence on the disease. 

2. The deficient illumination is due to 
the low illuminating power of the safety 
lamps generally used by coal miners, to 
the distance at which these lamps have to 
be placed from the objects which the miner 
has to look at, and to the great absorption of 
light by the coal and the coal dust covered 
surfaces. In addition to the effect of the 
coal dust or dirt in obscuring the lamp 
glasses, the choking of the wire gauze 
chimneys, and the presence of moisture or 
low oxygen percentage in the mine air, 
all reduce the light given by oil lamps, 
while failing voltage, poor bulbs or lack 
of proper attention have a similar effect on 
the illumination given by electric lamps. 

3. Workers at the coal face are more 
affected than other underground workers. 
and this appears to be due to the unrelieved 
blackness of the coal and the greater need 
for accurate vision. 

4. Distinct signs of Nystagmus are 
present in a large proportion of coal 
miners, though only in a small proportion 
do the symptoms ever become so severe 
as to cause even temporary incapacity 
for work underground. 

Incapacity due to nystagmus is rare 
among miners working with open lights, 
and everything possible should be done to 
make the standard of illumination of the 
objects looked at by the miner equal to 
that of an open light pit. This can be 
effected by greatly increasing (to about 
2 or 3 candles) the illuminating power 



of safety lamps as ordinarily used, or by 
the use of an electric light capable of 
being fixed on a miner's head belt v or 
other convenient position, so that the 
light is automatically brought nearer the 
working area and does not impair clear 
vision by shining directly into the eyes. 
At parts of the pit other than the coal 
face the visibility of objects can be greatly 
increased by whitewashing, and by the 
stone dusting obligatory for the prevention 
of explosions. The Committee believe 
that by the application of theee remedial 
miners nystagmus of sufficient severity to 
cause disablement can, by degrees, be 
entirely prevented. 

Historical Survey of the Disease. 
Dr. Llewellyn's general report contains 
first an historical survey of the disease. 
Even in the period from 1878 to 1891 
there were some (including Romiee and 
Court) who believed that deficient light 
was the essential factor in causing 
nystagmus. The matter was brought 
prominently forward in 1907 when the 
report of the Departmental Committee 
on Industrial Diseases led to the inclusion 
of the disease among those scheduled 
under the Workmen's Compensation Act 
of 1906. In 1912 the Oxford Ophthal- 
mological Congress passed a resolution 
recognising deficient light as the chief 
factor — a result confirmed by the re- 
searches of Elworthy, Llewellyn, Ohm and 
Stassen, and particularly in Llewellyn's 
book, published in 1912. Discussions on 
the subject have since taken place before 
the North Staffordshire branch of the 
Institution of Mining Engineers (1920), 
the Illuminating Engineering Society 
(1920), and the International Congress 
of the Royal Institute of Public Health 
in Brussels in the same year. 

Incidence op the Disease and 
Economic Factors. 

In the next section of the report the 
incidence of the disease and economic 
factors are discussed. The accident rate 
per 1,000 underground workers steadily 

increased up to 1914, when the war 
made researches rather uncertain. The 
percentage of men who show signs of 
nystagmus has been variously given as 
ranging from 20-35 per cent. Probably 
25 per cent, of all men over 21 years work- 
ing underground could obtain a surgeon's 
certificate and be legally disabled ; how- 
ever, the psychic element of the disease 
(discussed in the report by Dr. Rivers) 
must also be considered. It appears 
probable that the total incapacity rate 
in the United Kingdom, France, Belgium 
and Germany is 0'2 per cent, of men 
employed underground. Meantime the 
amount of compensation paid for all 
industrial diseases in the mining industry 
has risen from £13,382 in 1908 to £343,094 
in 1920. This increase has been due 
almost entirely to nystagmus : in 1920 
probably nearly £300,000 was paid in 
compensation for this disease alone. 
Apart from this direct expense there is 
the economic loss involved in absence of 
coal output of some 6,000 men, which, 
with the sum spent in compensation, 
involves a loss of approximately 
£1,000,000 per annum. 

One striking fact is that the prevalence 
of the disease is seasonable. It is most 
prevalent in the dark winter months, and 
the bright summer months bring about 
improvement in some cases. Expressed 
as a percentage the prevalence is 33 per 
cent., 20 per cent., 22 per cent, and 25 
per cent, in the four quarters of the year, 
thus showing again that liyht is the 
essential factor. Dr. Llewellyn next 
gives a detailed account of the symptoms 
of the disease. 

Dr. Llewellyn discusses various in- 
fluential factors, such as nature of mine, 
occupation, etc. The most vital factor 
is illumination, which is dealt with in 
the next portion of the report. 

The essential fact is that nystagmus is 
uncommon in purely naked light districts 
but is found in all places where safety 
lamps have to be used. It is, for instance, 



common in Belgium, France and Ger- 
many, where safety lamps are almost 
universally employed ; but in America, 
where open lights and electric cap lamps 
are usual, and in Japan, where acetylene 
lamps are used, the disease is rare. 

Relation between Miners'. Nystagmus 
and Inadequate Illumination. 

The actual brightness at the coal face 
depends on : ( 1 ) candlepower of source 
of light used, (2) distance at which light 
has to be placed from working area, 

(3) surface brightness of surroundings, and 

(4) composition of the air at coal face. 
Although there has been an advance in 
the candlepower of lamps recently, it is 
only within the last year or so that two 
candlepower has been attained. In his 
report Dr. Llewellyn reproduces the 
diagrams showing distribution of light 
from Hailwood's and Oldham lamps, 
which appeared originally in his paper 
before the Illuminating Engineering 
Society. As illustrating the effect of use 
he quotes tests showing a reduction of 
from 06 to 0'48 for an oil lamp and - 8 
to 0'58 for an electric lamp ; these figures 
represent the mean of tests on 531 lamps. 
Deposits of grime, falling pressure of the 
battery (with electric lamps) and dimi- 
nution of oxygen in the air (with oil 
lamps), all tend to reduce candlepower. 
Another source of irregularity is the 
variation in electric lamps. In one set 
of tests the same type of electric cap lamp 
gave 1*4 candles with one set of bulbs 
and 0*8 with another. 

The average illumination at the coal 
face in safety lam]) pits is only about 
(V018 foot-candles, as compared with 009 
in candle pits. In practice the illu- 
mination may even be less than 1/100 of 
a foot-candle. Of this feeble illumination 
a great deal is absorbed by the dark 
surface of the coal, which may absorb 
97 per cent, of the light. In a series of 
collieries where the candlepower of lamps 
varied from 066 down to (J-39 (after use) 
the nystagmus prevalence increased with 

the diminishing values of light, from 0*36 
to 075. Apart from the desirability of 
increasing the candlepower of lamps, the 
possibility of using cap- amps, thus 
enabling the source to be brought much 
closer to the working surface, is of 

Elworthy has suggested that incurable 
nystagmus might be due to ultra-violet 
light and suggested the use of yellow 
filters. Such screens reduce the light by 
10 to 20 per cent., and their beneficial 
effect requires further investigation. 
Experience of ultra-violet light in sources 
of great intensity is not applicable to the 
conditions of very feeble illumination 
customary in mines. 

Effect of Glare. 
Although glare is usually associated 
with lights of high intensity, in the low 
illumination of a coal mine any direct 
rays striking the eye may produce incon- 
venience. One objection raised to the 
cap lamp is that the bright light annoys 
men working alongside. Many colliers 
work in a reclining position with the lamp 
at their feet, so that the light shines 
obliquely into their eyes, which has incon- 
venient results. Painting or frosting pait 
of the lamp glass is of service in prevent- 
ing annoyance to other workmen during 
the journey to the face. Mr. McLoughlin, 
of Brancepeth, paints the pillars, lamp 
rings into which the pillars fit, and 2 5 
of the lamp glass with white enamel 
paint. Twelve men, suffering from 
nystagmus, when supplied with these 
lamps were able to continue work at the 
coal face. Workmen, however, prefer a 
detachable metal shade when travelling 
from and to the coal fare ; enamelling 
on the glass of lamps rapidly wears away. 
If the metal work pillars and rings of 
electric lamps are enamelled white, men 
agree that this improves the light. Mr. 
Peasegood has decided to enamel the 
standards of his electric lamps, but to 
leave the lamp glass untouched ; on the 
electric lamp the enamel lasts six weeks. 



Effect of Introduction of Lamps of 
Higher Candlepower. 

Taking into account the fact that the 
candle can be placed nearer the work 
remains constant throughout the shift 
and casts no shadows, it is concluded 
that the collier in a naked light pit works 
in an illumination five to ten times as 
great as that obtaining in a safety lamp 
mine. The discrepancy has, however, 
been diminished by the introduction of 
electric lamps and great improvements 
in oil lamps. 

The following figures are presented for 
Rhymney Valley :— 

Safety Lamp Pits 
Candle Pits 



6 3 



at coal face 

in foot- 



The occurrence of the two classes of 
pits has provided material for an ex- 
periment in illumination which has lasted 
TO years. Improvement in illumination 
has apparently not always been followed 
by a diminution in disease. But the 
much wider knowledge of the disease and 
improvements in diagnosis have led to 
more cases being recorded. Also the 
benefit of increased illumination is only 
felt gradually as the disease has a gradual 
onset. In the Yorkshire coalfield, where 
the proportion of electric lamps varies 
from 25 to 75 per cent., the percentage of 
nystagmus has materially decreased in 
the period 1913 — 1919, whereas in the 
United Kingdom during the same period 
the incidence has increased slightly. 
Opinions are quoted to the effect that 
the introduction of electric lamps has had 
good results. In particular Elworthy's 
results for Ebbw Vale are striking. In 
1914 the incidence was - 73. After im- 
proved ventilation and electric lamps were 
introduced, the figure in 1914 was only 
0-22. By 1920, when over 6,000 electric 
lamps were in use, it was only 016. In 

1909-1911 the incidence rate was four 
times that for South Wales, in 1920 it 
was only half. 

Electric Cap Lamps. 
Experiments with electric cap lamps 
have been made in four collieries in 
North Staffordshire. Following experi- 
ments with 130 lamps it is concluded : — 

(1) In pits of ordinary depth, where 
men are able to wear caps in comfort, 
the lamps can be used with success at 
the coal face. In hot pits, where the 
men work almost stripped, the lamps are 
not so satisfactory. 

(2) The lamps can be used in the road- 
way in all classes of pits. 

(3) For special work (building a stop- 
ping, quick examination of roof, for 
hauliers) the lamp is superior to the 
ordinary pattern. 

(4) To obtain the best results men 
should wear a special cap, the leather 
pit cap being perhaps the best pattern. 

Some remarks by Mr. Gardiner, 
manager of the Stafford Coal and Iron 
Co., on the " Oldham electric cap lamp " 
are quoted. The lamps were issued to 
persons in different occupations and found 
to be quite suitable, except by one or 
two older men. Both arms could be 
kept free and the light concentrated on 
the spot looked at. At first the weight 
of the lamp on the head causes slight 
discomfort, but this soon disappears. The 
weight of the accumulator is scarcely 
felt, but a man stripped may find some 
discomfort from the chafing of the strap 
on the skin. 

Finally Dr. Llewellyn discusses the 
effect of various other factors, such as 
age, hereditary disposition, alcohol, etc. 
Dr. J. S. Haldane has shown that the 
constitution of air in mines has no 
influence in causing the disease. The 
report is concluded by a series of 
references, amongst which several issues 
of The Illuminating Engineer are 



Jllumtnating lEngincertng Society. 

(Founded in London, 1909.) 


Tel. No. Victoria 5215. 


The Lighting of Public Buildings. 

The discussion before the joint meeting of the Illuminating Engineering 
Society and the Royal Institute of British Architects on March 28th was 
opened by a most comprehensive paper by Dr. E. H. Rayner, Mr. J. W. T 
Walsh, and Mr. H. Buckley, of the National Physical Laboratory, Sir 
Joseph Petavel, Director of the Laboratory, kindly presiding. 

In this issue we are reproducing in full this valuable summary of 
experimental work, leaving to our next number the ensuing discussion, 
including the account of methods of lighting in various decorative interiors 
furnished by Capt. W. J. Liberty. 

The experiments described, arising out of a request for information 
on the lighting of public buildings conveyed by H.M. Office of Works, 
aimed at the provision of an average illumination of about 4 foot-candles. 
From the tabular data appearing on page 120 it will be seen that the desired 
conditions were obtained by a variety of different methods, semi-indirect 
lighting being generally employed. The record of these experiments 
should prove most valuable for reference purposes, and the Office of Works 
have undoubtedly done a useful service in arranging for these tests to be 
made, and afterwards kindly granting permission for a summary of the 
results to be placed before the Society. 

b 2 


The most striking feature of the paper, which was completely borne 
out by the discussion, is the recognition of 4 foot-candles as a desirable 
initial average illumination in public offices. In view of the fact that some 
deterioration must needs occur in course of time this initial value does not 
appear excessive. It is common knowledge that in the past very much 
lower values have been prevalent, and it is largely due to the educational 
work of the Illuminating Engineering Society that there has been a sub- 
stantial improvement during recent years. In this case it was decided to 
study chiefly semi-indirect methods, which have certain advantages, but 
also some drawbacks. Deposits of dust in bowls used for semi-indirect 
lighting and gradual discoloration of the ceiling lead to a progressive 
diminution in the available illumination. Hence it is of great importance, 
in buildings lighted by this method, that fittings should be cleaned regularly 
and that the paint or distemper on walls and ceilings should be periodically 
renewed. It would be interesting, in the future, to have similar data 
presented relating to direct lighting, which is less affected by such con- 
ditions. It would, however, be necessary to ensure that equally good 
results as regards avoidance of glare are obtained. The low intrinsic 
brightness of the lighting units, not exceeding 2*5 candlepower per square 
inch, wa^ undoubtedly a good feature in this series of installations. 

The results show that estimates of resultant illumination with a given 
consumption of energy can be foretold with sufficient accuracy, though 
some latitude in this respect must be allowed. One source of uncertainty 
is doubtless the fact that at present opal bowls vary appreciably in optical 
qualities, and this necessarily affects the distribution of illumination. 

The section of the paper referring to these experiments should be 
useful to architects, and the two later portions, referring to methods of 
lighting picture galleries and the experimental building being erected at 
the National Physical Laboratory, also deserve study. The experiments 
on the natural lighting of picture galleries arose out of a design submitted 
by Sir Frank Baines, of H.M. Office of Works, for the purpose of avoiding 
the inconvenient reflections of light in the glass of pictures, which has 
proved a constant source of trouble. The method suggested, while occasion- 
ing some loss of daylight, seems to effect a material improvement in this 

The special experimental building erected in the grounds of the N.P.L. 
for the purpose of facilitating the study of lighting problems is unique, 
and we hope that the fullest use will be made of this valuable equipment 
by those desiring information on this subject. Much has been learned in 
connection with the quantitative treatment of daylight problems since 
the Society commenced its work, but the predetermination of " daylight 
factors " and resultant conditions of illumination has always been a matter 
of some difficulty. The existence of this experimental building should, 
however, enable the N.P.L. to deal with such problems on a scientific basis, 
and their advice should prove of great value. 

In conclusion we should like to take this opportunity of expressing 
our appreciation of the precedent established by the participation of the 
Royal Institute of British Architects in this joint discussion, which we 
hope will be the preliminary to further co-operation in the future. 


Illuminating Engineering and Industrial Safety. 

The steady progress of the British Industrial " Safety First " Association 
will be welcomed by all who are familiar with the good work that this 
body is doing. This work is of interest to illuminating engineers not only 
because of the intimate relation between good lighting and the prevention 
of accidents, but because the educational methods employed have much 
in common with those adopted by the Illuminating Engineering Society 
in advancing the cause of good lighting. 

The revival of Safety First, the journal of the Association, in a new 
and expanded form, marks a new stage in the progress of the movement. 
It contains articles written from different points of view, including a record 
of the history of the movement by Mr. H. E. Blain, an account of experiences 
at Port Sunlight by Lord Leverhulme, and a consideration of " Safety 
First " as an adjunct to the Factory Acts by Mr. Gerald Bellhouse (H.M. 
Deputy Chief Inspector of Factories). Attention is also drawn to the 
useful " Accident Prevention Pamphlet " issued by the Association which 
includes forms for the recording of statistics on accidents of all kinds. 
The writer also contributed, by request, an article on " Industrial Accidents 
and Inadequate Lighting," pointing out the need for reliable statistics in 
this field. In view of the number of forms that manufacturers are called 
upon to fill in one is reluctant to make additions. For the benefit of those 
specially interested in the relation between inadequate lighting and the 
prevalence of accidents it may, however, be recalled that suitable forms 
for use in studying this subject were published in The Illuminating 
Engineer for January 1918. This branch of the general classification of 
accidents will doubtless receive attention from the British Industrial 
" Safety First " Association in due course. Meantime we should like to 
take this opportunity of recording our appreciation of the support given 
to the movement for improved industrial lighting, whenever opportunity 
has arisen. Readers will recall especially the technical pamphlet on 
industrial lighting prepared by the writer and widely distributed by the 

The record of many firms who have adopted " Safety First " methods 
is impressive. Perhaps the most remarkable is that of Port Sunlight, where, 
it is stated, the " Safety First " movement originated, being afterwards 
actively taken up in the United States. Statistics furnished by Lord 
Leverhulme show that in the period 1907-1920 the number of accidents 
reported to the Home Office has diminished alniost invariably year by 
year, and now stands at the low figure of 7*8 per 1,000 workers, as compared 
with 25 per 1,000 originally. In other cases mentioned by Mr. Blain 
diminutions in accidents ranging from 21 to 75 per cent, have been made 
in quite a short period, and the reduction tends to be progressive as the 
effect of " Safety First " methods is cumulative. 

We are informed that some Insurance companies allow substantial 
reductions in premiums, corresponding with the diminution in accidents 
achieved during the year, and have even been prepared to make concessions 
immediately to firms that have joined the Association. We believe that 
if the relation between inadequate lighting and accidents could be 
traced with exactitude, insurance concerns might be disposed to allow 
reductions to manufacturing firms whose lighting arrangements had been 
brought up to the requisite modern standard of efficiency. 


The Use of Artificial llluminants in Motion Picture Studios. 

In the discussion on the Lighting of Kinema Studios before the Illumin- 
ating Engineering Society last year* it became apparent that there were 
many aspects of the subject on which fuller data were needed. The Society 
accordingly formed a Joint Committee to inquire further into the subject, 
and we have since been endeavouring to obtain information from various 
sources. Amongst those approached on the subject, Dr. Kenneth Mees 
of the Eastman Kodak Company, expressed his interest in the inquiry and 
kindly promised to furnish some data. We have recently received from 
him a copy of a most valuable and comprehensive report on " The Use of 
Artificial llluminants in Motion Picture Studios," by Mr. L. A. Jones, who 
is associated with the Kodak Laboratory. We propose to deal fully with 
this paper in due course in the journal, and meantime we take the oppor- 
tunity of giving an idea of its contents. 

The treatment falls naturally into two divisions, (a) the characteristic 
of photographic materials and their response to radiation, (b) the character- 
istics of the human eye and the possibility of injury to this organ arising 
through excessive intensity or special forms of radiation emitted by the 
illuminants used. 

It is remarked that a considerable amount of information exists, but 
its interpretation needs care, and the use of a logical and scientific system 
of terminology and units is essential. Accordingly the chief photometric 
units are defined in terms approved by the Illuminating Engineering 
Society in the United States. The various photographic quantities are 
also treated in detail, and suitable formulae relating photographic effect 
to intensity and wavelength are developed. Finally a diagram is furnished 
illustrating the manner in which the eye is affected by glare, and indicating 
the limits of desirable contrast and brightness. 

The study of photographic effect is a somewhat complex matter. It 
is interesting to observe, for instance, that the relation between density 
of image and log. exposure is only a straight line over a certain range. In 
weighing the advantages of various illuminants due regard must be paid 
to the nature of the film or plate vised, and the tabular data on this point 
are furnished for ordinary, orthochromatic and panchromatic materials. 
A curve for the transmission of glass throughout the spectrum is also 
furnished — a useful item in view of the discussion as to the extent to which 
ultraviolet rays are absorbed by the camera lens. 

Enough has been said to show that the paper should be of great value 
for purposes of reference, and it contains a useful bibliography. As regards 
the question of possible injury to the eyes, it is satisfactory to observe that 
the author fully endorses the views that have been expressed in this journal 
regarding the advisability of equipping powerful illuminants used in studios 
with suitable diffusing shades. It appears that if proper precautions in 
this respect are observed the risk of injury to the normal eye can be reduced 
to quite small dimensions. 

Leon Gaster. 

* Illum. Eng., Feb. igzi. 




Zbc 3llummating Engineering Society 

(Founded in London, 19090 

The Illuminating Engineering Society is not, as a body, responsible 
for the opinions expressed by individual authors or speakers. 


(Joint Discussion with the Royal Institute of British Architects.) 

(Proceedings at a joint meeting, arranged by the Illuminating Engineering Society in conjunction 
with the Royal Institute of British Architects, held at the House of the Royal Society of Arts, 
18, John Street, Adelphi, W.C., at 8 p.m., on Tuesday, March 28th, 1922.) 

Mr. J. W. T. Walsh and Mr. H. Buckley 

A meeting was held at the House of the 
Royal Society of Arts (18, John Street, 
Adelphi, London), at 8 p.m. on Tuesday, 
March 28th, the chair being taken by 
Sir Joseph Petavel, Director of the 
National Physical Laboratory. 

The Minutes of the last meeting having 
been taken as read, the Hon. Secretary 
read out the names of the following 
applicants for membership : — 

Ordinary Member : — - 
Everett, A. G. 

Corresponding Member : — 
Nishima, Y. . . 

The names of applicants announced at 
the last meeting of the Society* were read 
for a second time, and these gentlemen 
were formally declared members of the 

The Chairman, in a short introductory 
address, recalled the work carried out at 
the National Physical Laboratory on the 
subject of discussion, and mentioned that 
the discussion had been arranged jointly 
with the Royal Institute of British 
Architects. He then called upon Dr. 
E. H. Rayxer to present the paper on 
"The Lighting of Public Buildings," pre- 
pared by him in collaboration with 

* Illum. Eng., Feb. 1922 ; p. 41. 

(also of the National Physical Laboratory). 
Subsequently the Chairman called 
upon Capt. W. J. Liberty, Public Light- 
ing Inspector to the City of London, to 
present some data on the Lighting of 
Decorative Interiors, which included the 
Guildhall, the Marylebone Town Hall, 
the new Port of London building and the 
Middlesex Session House. 

Technical Assistant, Cosmos Lamp Works, 
Brimsdown, Middlesex. 

Lecturer in Electrical Engineering, Imperial 
University, Tokyo, Japan. 

In the ensuing discussion Mr. F. A. 
Llewellyn (H.M. Office of Works), Mr. 
P. J. Waldram, Major H. C. Gunton 
(Post Office), Mr. Chas. Baker (Elec. 
Engineer to the L.C.C.), Mr. G. Campbell, 
Mr. Haydn T. Harrison, Capt. E. 
Stroud, Mr. A. Cuxxixgton, Mr. 
Ramsey (H.M. Office of Works), took 

Mr. J. W. T. Walsh having briefly 
replied to points raised in the discussion, 
a vote of thanks to the authors and the 
Chairman concluded the proceedings, 
after which it was announced that the 
next meeting would be held at the end of 
April, when there would be a discussion 
on " The Uses of Light in Hospitals." 






I ■ ■ ■ 1 ■ n i 




pensions oftices ■ ACTON 






Fig. 1. — Showing dimensions of one of the large rooms in the new building of the Ministry of 
Pensions at Acton, where the experiments were conducted. 




An Account of Experimental Work and Results 

By E. H. Rayner, Sc.D., J. W. T. Walsh, M.A., M.Sc, and H. Buckley, B.Sc, 
of the National Physical Laboratory. 

(Presented at the joint meeting of the Illuminating Engineering Society and the Royal Institute 
of British Architects held at the House of the Roval Society of Arts, 18, John Street, Adelphi, 
London, W.C., at 8 p.m., on Tuesday, March 28th, 1922.)" 

ments which aimed at providing an 
initial average illumination' over the 
whole room of about 4 foot-candles. 

Experimental Arrangements. 

For the purposes of the experiments 
one-half of one of the large rooms at 
Acton, the dimensions of which are 



The experiments described in this 
paper arose out of the request of H.M. 
Office of Works for information which 

Fig. 1a.- 

-Showing present condition of room at the Ministry of Pensions building, Acton ; 
photo taken entirely by artificial light. 

would assist them in drawing up a 
specification for lighting installations 
at the new building of the Ministry of 
Pensions at Acton. The particular pro- 
blem under investigation was the lighting 
of very large rooms which it was antici- 
pated would be used for the work of 
large numbers of clerical staff. 

The semi-indirect, which was con- 
sidered to be the best method of lighting 
such rooms, was adopted in the experi- 

170 ft. by 37 ft, 6 in. by 12 ft. 6 in., was 
prepared and wired by H.M. Office of 
Works for the installation of various 
lighting systems. Several manufacturers 
kindly placed selections of their fittings 
at the disposal of H.M.O.W. and the 
N.P.L., while H.M.O.W. carried out 
decoration schemes suggested by the 

Some idea of the room used in this 
work can be obtained from Fig. 1 , which 



shows it in plan and elevation, and from 
Fig. 1a. Structural details call for a 
certain amount of consideration, as they 
imposed important restrictions on the 
arrangement and choice of fittings. The 
dimensions were 80 ft. by 37 ft. 6 in. by 
12 ft. 6 in., and the ceiling was crossed 
by a series of girders 15 in. deep, which 
divided the room into eight bays each 

have been desirable, if a clear expanse 
of ceiling had been available. 

The windows (8 ft. 6 in. by 5 ft.), 
reaching to within about 15 in. of the 
ceiling, were at 10 ft. centres in the 
middle of each bay. For the test they 
were covered with black boards repre- 
senting the conditions existing when 
either no blinds at all or black blinds are 





26 24 



5 18 

16 14 

12 I 

> 8 


4 2 

■,— T 










,3 , 


, ! , 





80' -0- 


Fig. 2. 

37-<p' N 



22 2D 



|— l(K>— 

I !■-€>' 


J i!°± 


Fig. 3. 

10 ft. wide. In addition, each girder 
was supported by a vertical stanchion 
9 in. wide, at a distance of 15 ft. 6 in. 
from one of the long walls. If due 
regard to symmetry were observed, the 
division of the ceiling in the manner 
indicated limited very much the freedom 
of arrangement of the various fittings, 
while the depth of the girders below the 
ceiling prevented the use of fittings 
actually on the ceiling, or even the 
placing of them at such heights as might 

used. White cloths were also provided 
to imitate the behaviour of light-coloured 
blinds. Experiments were made with 
and without these cloths., so as to 
evaluate the effect of blinds on the 

The working plane was taken at a 
height of 2 ft. 6 in. from the floor. In 
certain rooms at Acton the height is 
only lift. 6 in. Information likely to 
be of value in selecting installations for 
these rooms was obtained by taking 



measurements at a height of 3 ft. 6 in. 
The justification for this lies in the fact 
that the portions of the walls and floor 
below the working plane exert little 
effect on its illumination. In the most 
favourable case possible with white 
walls and very light floor, this effect is 
believed to be less than 5 per cent., while 
in the cases under consideration the 
floor was fairly dark having a reflection 
ratio of about 35 per cent. 

Experimental Procedure. 

Illumination measurements with either 
a lumeter or luxometer were made along 
selected lines in the room as shown in 
Fig. 2. Twenty-six observations were 
taken in each row and, in addition, 
twelve observations in each of two or 
more cross lines were taken. Later, 
in the course of the experiments, the 
arrangement of the points of observation 
was changed and the points shown 
in Fig. 3 were adopted. The reason for 
this change is discussed later in the 

The average illumination over the 
whole room was taken as the mean of 
all the observations (100 or more) ; 
the total watts used in each installation 
were also noted. In addition, observa- 
tions of surface brightness of the visible 
light sources and the reflection ratios 
of the decorations were made. 

The power supply at Acton was 
direct current at 230 volts, and was 
subject to considerable variation from 
minute to minute. It was found 
necessary in the latter half of the 
experiments to have someone con- 
tinuously adjusting the voltage. The 
lamps used were straight from stock. 
Tests on a selection of those used, which 
may have burned anything up to 50 
hours, were made at the end of the 
experiments and their efficiencies and 
polar curves determined. 

The fittings are shown diagrammatic- 
ally in Fig. 4, their arrangement in the 
various installations in Figs. 5 to 13, 
and their polar curves in Figs. 14 to 22. 

Results of Experiments. 

The results of the experiments are 
given graphically in the diagrams referred 
to as Installations I. to XVI., which, 
it is hoped, are self-explanatory. Most 

of the information relative to the various 
installations is to be found in these 
figures, so it will be sufficient in the 
body of the paper to refer to points of 
interest which arise from the considera- 
tion of the results. 

Notes on the Installations. 

Installations I. to VII. refer to con- 
ditions of the walls and ceiling known 
as Decoration I. This is sufficiently 
described by the following data : — 

Ceiling, distempered white ; reflection 

ratio, 80 per cent. 
Walls, distempered white ; reflection 

ratio, 70 per cent. 
Blinds, dirty white ; reflection ratio, 

55 per cent. 

The screen forming one end of the 
room was rather dirty, its reflection 
ratio being about 50 per cent., so that 
the relative areas of the walls having 
reflection ratios of 70 per cent, and 20 per 
cent, were in proportion of 7 to 2. 

Installations VIII. and IX. refer to 
conditions of the walls and ceiling known 
as Decoration II. : — 

Ceiling, white ; reflection ratio, 80 per 

Walls, buff ; reflection ratio, 60 per 

Blinds, as before. 

Installations X. to XIII. with 
Decoration III. : — 

Ceiling, white ; reflection ratio, 80 per 

Top freize 2' 6" deep, white ; reflection 

ratio, 80 per cent. 
Walls, bluish grey ; reflection ratio, 

25 per cent. 
Blinds, as before. 

Installations XIV. to XVI. with 
Decoration IV. : — 

Ceiling, white ; reflection ratio, 80 per 

Top freize 1 ft. deep, white ; reflection 

ratio, 80 per cent. 
Walls (upper portion), buff ; reflection 

ratio, 42 per cent. 
Dado, bluish grey ; reflection ratio, 

25 per cent. 
Blinds, as before. 











Fio. 5. 












Fro. 6. 






















Fio. 7. 
Diagrams showing positions of fittings in the various installations. 



The difference in illumination pro- 
duced by the absence or presence of 
blinds is shown in the results of Installa- 
tions I. and la., and again in Installations 
V. and Va. 

From Decoration II. to III. bv 
Installations IX. and X., and also 
by VIII. and XI. 

From Decoration III. to IV. by 

(A) 14' Opal Bowl, also with daylight bowl 


B) to - Opal bowl with over reflector. 

O) ii Opal Bowl with over Reflector 

IE)i4'0pal bowl with over Reflector 

(?) 7' opal bowl 

(h) Indirect Fitting 

(Cal ir Opal bowl with over Reflector 

Fig. 4. 

The effect of a change of decoration Installations XIII. and XIV., and 

on the same illumination system is also by XHIa. and XlVa. 

exhibited by the foUowing installations :— The effect of different heights of 

From Decoration I. to II. by Installa- room (obtained by altering the height 

tions VII. and VIII. of the working plane) is shown in 





•■ ■ 



Fig. 8. 




•■ ■■ 1 


Fig. 9. 






















Fig. 10. 

Diagrams showing positions of fittings in the various installations. 


• ' 



— • 

— • 



— • — 

— • — 





Fig. 11. 






— . 




•-- ■ 


Fig. 12. 




*-- — 








Fig. 13. 

Diagrams showing positions of fittings in the various installations. 



Fig. 14. — Polar curve of 250 v. 150 w. gas- 
filled lamp in conjunction with Semi- 
indirect 14 in. Opal Bowl shown in Fig. 4a 
(lamp filament 2 in. below plane of top of 

Fig. 15. — Polar curve of 230 v. 150 w. gas- 
filled lamp in conjunction with Scmi- 
indircct 14 in. Opal Bowl shown in Fig. \\ 
(lamp filament 1 in. below plane of rim 
of bowl). 

Fig. 16.— Polar Curve of 230 v. 100 w. gas- 
filled lamp in conjunction with Semi- 
indirect 10 in. Opal Bowl and Over Re- 
flector shown in Fig. 4b (Over Reflector 
just full of light). 

Fig. 17.— Polar curve of 230 v. 150 w. gasfilled 
lamp in conjunction with Semi-indirect 
14 in. thick Translucent Bowl shown in 
Fig. 4o (lamp filament 2 in. below plane 
of top of bowl). 

Fig. 18.— Polar curve of 230 v. 150 w. gas- 
filled lamp in conjunction with Semi- 
indirect 11 in. Opal Bowl and 23 in. Over 
Reflector shown in Fig. 4d (lamp filament 
2 in below plane of top of bowl). 



Installations XIII. and Xllla., and also 
in XIV. and XlVa. 

An indirect lighting system was 
employed in connection with Decorations 
I. and II., and the results are given 
under Installations XV. and XVI. 

illumination was measured was not so 
sufficiently representative of the whole 
room as it might have been. As a result 
a new system of lines L, M, N, and P, 
were marked out (Fig. 3), and it was 
considered that measurements along these 

Fig. 19.— Polar curve of 230 v. 200 w. gas- Fig. 
filled lamp in conjunction with Semi- 
indirect 14 in. Opal Bowl and Over Reflector 
shown in Fig. 4e (lamp filament 2| in. 
below plane of top of bowl). 

20.— Polar curve of 230 v. 150 w. gasfilled 
lamp in conjunction with Semi-indirect 7 in. 
Opal Bowl shown in Fig, 4f (lamp filament 
1 in. below plane of rim of bowl). 

Fig. 21. — Polar curve of 230 v. 150 w. gas- 
filled lamp in conjunction with Semi- 
indirect 11 in. Opal Bowl and 23 in. Over 
Reflector shown in Fig. 4g (lamp filament 
in plane of rim of bowl). 

Fig. 22.— Polar curve of 230 v. 200 w. gas- 
tilled lamp in conjunction with Indirect 
Silvered Reflector shown in Fig. 4h (lamp 
filament 1 in. below plane of rim of bowl). 

Note on the Change in the Selection of the 
Lines along which the Illumination 
was Measured. 

After Installation III. had been com- 
pleted, it was realised that possibly the 
choice of the lines along which the 

rows, when averaged, would give a 
better mean than the others. 

In the following inset-sheets the com- 
plete data relating to this set of in- 
stallations are assembled in diagram 



Installation I. 

Decoration I. Installation III. 

Decoration I. 

fittings. Bight semi-indirect 14 in. 
opal bowls with 200 watt lamps, arranged 
as shown in Fig. 5. 

The average illumination was found 
to be 4"3 foot-candles for a power con- 
sumption of 1,605 watts. 

Very noticeable shadow effects were 
produced on the ceiling due to a lamp 
in one bay casting a shadow of the 
neighbouring girder on to the ceiling 
of the next bay. The shadows of the 
vertical stanchions were also very 

Tlic diversity factor of the illumination 
was very high. It was concluded that 
the lighting units of this type were not 
sufficient to cive an even approximately 
uniform illumination. 

Installation la. Decoration la. 

Fittings. — As in I. 

In this case the white cloths over the 
windows were removed, and the black 
boards of reflection ratio 14 per cent. 
took their place. The effect on the 
average illumination was a reduction 
of 7 per cent, from 43 foot-candles to 
40 foot-candles. The illumination along 
the middle of the room (row B) was 
practically unaltered, so that the main 
effect of the absence of blinds was 
confined to the regions near the walls, 
as would be expected. 

Installation II. 

Decoration I. 

Fittings. — Twelve semi-indirect 14 in. 
opal bowls with 200 watt lamps. 

The arrangement of the fittings is 
shown in Fig. 6. The average illumina- 
tion was found to be 4*1 foot-candles 
for an expenditure of 1,900 watts. The 
ceiling still showed shadow effects, but 
they were not so objectionable as in the 
last installation. The effect of raising 
the lamps in the bowls was to spread 
the light more uniformly over the ceiling. 
The walls exhibited a frieze of brighter 
illumination from about 2 ft. 6 in. from 
the ceiling upwards. No pronounced 
shadows were caused by the vertical 

Fittings. — Twelve semi-indirect 14 in. 
bluish opal bowls with 150 watt lamps, 
arranged as shown in Fig. 6. 

This installation was the same as the 
last, except that the opal bowls were 
replaced by bowls in which, in addition 
to the flashed opal, there was a layer 
of slightly blue <_ r lass to give the light 
a slight suggestion of daylight. Tin- 
results were very similar to the last 
except that they are in all cases lower, 
owing to the absorption by the blue glass. 
The average illumination was 3*8 foot- 
candh's (compared with 4 - l foot-candles) 
for a power expenditure of 1,945 watts. 

Installation IV. 

Decoration I. 

Fittings.- Twenty semi-indirect loin, 
opal bowls and 23 in. over reflectors with 
100 watt lamps arranged as shown in 

Fig. 7. 

The average illumination was found 
to be 36 foot-candles for a power con- 
sumption of 2,070 watts, and was very 
uniform. Very slight shadow effects 
were visible, and the ceiling was uniformly 
illuminated to about 1 foot-candle, 
no direct light reaching it at all. 

The illumination along line L was 
on the low side, particularly in the 
middle. This could be remedied by 
bringing the two outside rows a little 
nearer the wall. A movement of 1 ft. 
in the case of the row nearest the wall 
and 6 in. in the case of the next would 
probably bring up the average along 
line L to at least 35 foot-candles without 
affecting any other lines too much. 
It should be noted that the efficiency of 
the 230 volt 100 watt lamps used was 
very low, viz., l - 26 watts per candle 

Installation V. 

Decoration I. 

Fittings. — Twelve semi-indirect 14 in. 
thick opal bowls with 150 watt lamps, 
arranged as shown in Fig. 8. 

The average illumination was found 
to be 4*3 foot-candles for an expenditure 
of 1,920 watts. The lighting appeared 
fairly uniform though the middle of the 








n I. 





a II. 


fe to 

5 of 

n II. 

7 in. 



room was a little too highly illuminated 

at the expense of the parts near the walls. 
This system compared very favourably 
with the somewhat similar systems of 
Installations II. and III. 

ceiling was qoI \ ery uniformly illuminated, 
direct lighl being incident on it both past 
the edge of the over reflector and through 
the hole in which the neck of the lamp 
was inserted. 

Installation Va. 

Fittings. — As in V. 

As in la, black boards of reflection 
ratio 14 per cent, took the place of the 
white cloths. For the whole room the 
result is that the absence of the blinds 
reduces the average illumination from 
43 foot-candles to 40 foot-candles — 
a reduction of 7 per cent. Rows L and M 
show diminutions in average candle- 
power from 3 - 8 foot-candles to 3'4 foot- 
candles, and from 43 foot-candles to 
40 foot-candles respectively. 

The averages along rows N and P 
remained the same, though it was 
anticipated that row P would show a 
drop in the average. This may be due 
to an unnoticed change in the voltage 
of the system. The uniformity of the 
lighting also suffered to a slight extent. 

Decoration la. Installation VII. 

Decoration I. 

Fittings. — Eight semi-indirect 14 in. 
opal bowls and over reflectors with 
200 watt lamps, arranged as shown in 
Fig. 10. 

These fittings were designed for use 
on the ceiling, but the traverse girders 
rendered this impossible, so with the 
object of having them in a permanent 
position for some time, they were fixed 
on the girders, and used with Decorations 
I., II. and III. 

The average illumination was 3" 4 foot- 
candles for 1,675 watts, and was 
moderately uniform. The opal bowls 
were very uneven in density, the highest 
illuminations being under those which 
permitted the filament to be seen. The 
ceiling was not very uniformly illuminated. 

Installation VI. 

Fittings. — Twelve semi-indirect 11 in. 
opal bowls and 23 in. over reflectors 
with 150 watt lamps, arranged as shown 
in Fig. 9. 

The average illumination was 39 foot- 
candles for an energy consumption of 
1,925 watts, but the uniformity was not 
very good. The lowest illuminations 
were found near the gap in the row of 
lamps in line L. With such an arrange- 
ment, with two lamps in one bay and 
one in the next, and an even number of 
bays to put them in, there is bound to be 
a lack of symmetry in the arrangement, 
unless some such system of spacing as was 
here adopted is used. It was considered 
that the arrangement 2, 1, 2, 1, 1, 2, 1 . _, 
would give better results than 2, 1, 2, 1, 
2, 1, 2, 1, as there is more opportunity 
of overlapping and consequent evening 
out of the illumination in the middle, than 
in other parts of the room. An improve- 
ment could have been made by moving 
the outside rows 1 ft. nearer the walls. 
The effect of such a movement is shown 
in Installations XII. and XIII. The 

Decoration I. Installation VIII. 

Decoration II. 

Fittings. — As in VII. 

The average illumination for the whole 
room was 3"5 foot-candles, or practically 
the same as before. A slight decrease 
was expected. The slight increase may 
be due to experimental error, or possibly 
deterioration of Decoration I., which 
consisted of only one coat of distemper 
on plaster. Experiments on a totally 
indirect system (Installations XV. and 
XVI.) did, however, confirm the slight 
increase. In any case it seems safe to 
deduce that in both systems the ceiling 
is the main reflecting surface as regards 
the production of illumination on the 
working plane, and that the walls play 
a very secondary part. Changes of 
10 per cent, in their reflection ratio, 
if this is high, do not alter the average 
illumination very much. 

Installation IX. 

Decoration II. 

Fittings. — Twelve semi-indirecl 7 in. 
opal howls with 150 watt lamps, arranged 
as shown in Fig. 11. 

I 2 



The average illumination was 3*9 
foot-candles for 1,900 watts. Improve- 
ment in uniformity would have resulted 
from placing the outside rows at about 
7 ft. from the walls. 

Installation X. Decoration m. 

Fittings— -As in IX. 

The average illumination was reduced 
from 39 foot-candles to 35 foot-candles — 
a reductio' of 12 per cent., the power 
expenditur being 1,900 watts. 

Installation XI. Decoration III. 

Fittings— As VII. and VIII. 

The average illumination was reduced 
from 35 foot-candles to 31 foot-candles — 
a reduction of about 12 per cent., con- 
firming the former value. 

Installation XII. 

Decoration III. 

Fittings. — Twelve semi-indirect 11 in. 
opal bowls and over reflectors with 
150 watt lamps, arranged as shown in 
Fig 11. 

The average illumination was 3 - l 
foot-candles for 1,910 watts, but the 
illumination on the outside lines was 
very low compared with the middle of the 
room, so the outside rows of lamps were 
moved nearer the walls. 

Installation XIII. 

Decoration III. 

Fittings.— As in XII., but arranged as 
shown in Fig. 12. 

The average illumination was reduced 
from 31 foot-candles to 3*0 foot-candles, 
but was much more uniform than in 
the last case. Line L still had a rather 
low illumination in places. It is probable 
that the fittings used in this case gave 
a too extensive distribution for a room 
with so small a ceiling height, and that 
a larger portion of the light given by 
this fitting was incident on the rather 
dark walls than is desirable in such 
cases. This fitting is probably most 
suitable for high rooms, 

Installation XHIa. Decoration III. 

Fittings. — As in XIII. For room 
11 ft. 6 in. high, working plane taken as 
3 ft. 6 in. from the floor. 

The average illumination was 3"0 foot- 
candles as compared with 3 - foot-candles. 
One would expect an increase, as the 
difference in the total light incident 
on the two planes is accounted for by 
the illumination of the part of the walls 
between the two planes. On the 
assumption that the average illumination 
of this portion of the walls was 15 foot- 
candles this was about 350 lumens. 
So that the percentage increase in 
the average illumination should have 

been -j£n& x i r a = * P er cent - I 9 . 000 
lumens is the total amount of light on 
the working plane). 

The uniformity of the illumination was 
reduced however. Points under lamps 
received an increased intensity of illumina- 
tion, but several points in between 
experienced a decrease. This decrease 
results from the fact that in certain 
cases the increment in illumination 
brought about by bringing the working 
plane nearer to the lamps is more than 
counterbalanced by the increased ob- 
liquity of incidence of the light. 

Installation XIV. 

Decoration IV. 

Fittings. — As in XIII. 

The average illumination was found 
to be reduced from 30 foot-candles to 
2 - 9 foot-candles. The increase which 
would be expected from the increase 
in the reflection ratio of the upper half 
of the walls seems to have been counter- 
balanced by the decrease due to the 
reduction in the freize from 2 ft. 6 in. to 
1 ft. in depth. 

Installation XlVa. 

Decoration IV. 

Fittings. — As in XIII. For room 
11 ft. 6 in. high, working plane taken at 
3 ft. 6 in. from the floor. 

The average illumination was found 
to be 30 foot-candles as compared with 
2*9 foot-candles — an increase of about 
3 per cent, confirming the results on the 
comparison of XIII. and XHIa. The 
uniformity was affected to about the 
same extent also. 

■) OJ — 



Installation XV. 

Decoration I. 

Fittings. — Nine indirect silvered re- 
flectors with 200 watt lamps, arranged 
as shown in Fig. 13 with the plane of the 
rim of the reflector 2 ft. from the ceiling. 

Only one-half of the room was con- 
sidered in the deduction of results. The 
average illumination was 4 - 7 foot-candles, 
but did not strike one as being as high 
as in several of the previous systems. 
The ceiling was very highly illuminated 
so that the rest appeared lower by 
contrast. There were no shadow effects 
except at the portion where the illumina- 
tion was dropping rapidly to zero. 

Installation XVI. 

Decoration II. 

Fitting. — As in XV. 

The average illumination was again 
4"7 foot-candles. This confirms the 
results of the measurements on Installa- 
tions VII. and VIII., where a very slight 
increase in average illumination was 
recorded as a result of changing the 

This concludes the portion of the paper 
dealing with the separate installations. 
The results of all the measurements 
are given in the curves. Individual 
members of these will probably show 
discrepancies when intercomparisons are 
made. Attention should, therefore, be 
paid more particularly to the average 
values obtained. 


It is difficult to draw conclusions from 
a series of lighting installations unless 
it is known definitely what are the 
precise conditions under which the con- 
clusions have to be applied. A number 
of installations have been put up in the 
experimental room and measurements 
of illumination have been correlated 
with the power consumption. In addition 
to the cost of power such considerations 
as the uniformity of the illumination, 
cost of maintenance of the decoration, 
cost of initial installation, etc., have 
to be taken into account. 

With the kind of ceiling available at 
Acton, it was difficult to say immediately 
whether it would be better to utilise 
fittings in which an artificial ceiling, 

i.e., an over reflector, was provided, or 
to make the best possible use of the 
existing ceiling. On comparing the 
fittings which use over reflectors and 
those which do not, the tests indicate 
that the former are usually at a slight 
disadvantage. In this connection the 
values of the watts per square foot for 
3 foot-candles illumination should be 
compared with the utilisation co-efficients 
of the various fittings. 

The relatively high watts per square 
foot for 3 foot-candles illumination in 
the case of Installation IV. is probably 
due to the low efficiency of 230 v. 100 w. 
lamps. The fittings used in Installation 
VI. gave results comparing very well 
with other fittings using the same 
decoration. The surface brightness of 
its opal bowls was considerably higher 
than most of the others, so that this 
result is probably due in part to a higher 
transmission of the bowls. 

The fittings used in Installations XII. 
to XHIa. were used with darker 
decorations, but by applying the known 
reduction in average illumination in 
passing from Decoration II. to Decoration 
III. they still appear to require more 
watts per square foot for 3 foot-candles 
than the other fittings using over 
reflectors. The opal bowls used in these 
fittings were rather dense, and were 
of lower intrinsic brightness than any 
others used. 

The tests indicate that the effect of 
light-coloured blinds as compared with 
dark-coloured blinds — or what is 
practically the same thing, no blinds at 
all — is not unimportant when light- 
coloured decorations are used. The 
difference between the average illumina- 
tions was of the order of 7 per cent. With 
darker decorations, where considerations 
of upkeep have resulted in the decision 
not to pay too much attention to the 
reflection ratio of the walls, this effect 
is not so large. 

As regards the rooms having a ceiling 
height of 11 ft. 6 in., the tests show that 
with the same decoration the difference 
is mainly one of uniformity, as would be 
expected. This difference can be partly 
eliminated by raising the fittings in the 
lower rooms, though the appearance of 
the ceiling may not be improved by 
such a change. 



As a result of considering installation 
costs, and the cost of current, renewals 
and decorations over a period of five 
years, H.M. Office of Works were led to 
the adoption of the installation scheme 
described as Installation II. in con- 

415 foot-candles, while the maximum 
and minimum were 5 - 5 foot-candles 
and 29 foot-candles respectively. 

It has been considered advisable to 
give the results of these experiments in 
full as there does not appear to be 

Summary of Results. 
Efficiency of Lamps 230 v. Gas-filled. 




mens per 









1 .-,! 1 













Ilium. 1 


per sq. ft. 







3 i.e. 

Per cent. 


Candles per 
sq. in. 


























12-160 W. 
















12160 W. 






































































0-6— 1-2 


























12-1 50W. 






(Mi— 1-2 















junction with the following decoration 

scheme : — 

ding, white; 80 per cent, reflection 

Walls, light buff ; 60 per cent, reflection 

Freize, white, 12 in. deep ; 80 per cent. 

reflection ratio. 

The rooms illuminated by this system 
were 170 ft. long by 37 ft". 6 in. wide; 
this resulted in the use of 26 14 in. 
opal bowls using 150 watt lamps spaced 
alternately two and one in each bay. 
'I he average initial illumination was 

any complete description of work of this 
nature in any of the technical journals, 
apart from that given by Ward Harrison 
and Earl A. Anderson, in a paper to the 
Illuminatinu Engineering Societv of New 
York in 1916. (Trans. 111. Ensr. Soc, 
N.Y., Vol. XI., page 67.) 

It is desired to express the thanks 
of the Laboratory to H.M. Office of 
Works, particularly Mr. A. C. Pallot, 
for their ready assistance in making all 
the arrangements and for their prompt- 
ness in carrying out the alterations in 
the many different installation and 
decoration schemes. 
















i / 


i / 










1- rti i 











As a result of studying the subject 
of the illumination of picture galleries 
one can hardly fail to arrive at the 
conclusion that the important factors, 
which ought to receive the most earnest 
consideration from those responsible for 
their construction, have been very largely 
neglected. The consequence is, that 
many of the most noted galleries, erected 
at great cost and housing pictures of 
inestimable value, are most woefully 
deficient in the essential features of 
design which make for good lighting ; 
and, except under special circumstances, 
picture lovers can seldom hope to see 
many of the world's masterpieces as 
they ought to be seen. 

The reason of this is that very often 
little or no consideration has been given 
to the effect of reflection of light from 
the surface of the glass covering the 
pictures. The glass is necessary for 
their preservation from dust and dirt, 
but, unfortunately for the spectator, 
in many pictures the light reflected from 
the glass may be equal to or greater than 
that reflected from the darker parts 
of the picture. Clear glass reflects some 
10 per cent, of the incident light ; and, 
though it may be possible to reduce this 
by a small amount, methods so far 
suggested would probably have dis- 
advantages considerably outweighing any 
benefits attainable. It is often impossible 
to study pictures properly, short of 
either removing the glass or of hanging 
a dark curtain behind the observer, as 
is commonly done when photographing 

The importance of the figure 10 men- 
tioned above will be realised from the 
fact that, while the reflection ratio of 
pictures of a light tone has been found 
to be as high as 50 per cent., that of 
Eembrandt's Portrait of Himself, for 
instance, is only 3*7 per cent., and of his 
Portrait of a Jewish Merchant only 1'5 
per cent. It follows that the brightness 
of the image of a visitor's dress of a light 
colour (having a reflection ratio of, say, 
80 per cent.) formed by reflection in the 
glazing which has a reflection ratio of 
10 per cent., will be 8 per cent. Thus the 
reflected image of the dress may not 

infrequently be brighter than the painted 
surface. It follows that in a very large 
number of cases the light reaching 
the eye by reflection in the glass from 
light-coloured objects will be of the 
same order of magnitude as that from 
the picture itself. In addition, it should 
be noted that the images seen in the 
glazing are not in the plane of the picture, 
so that there is constant effort necessary 
on the part of the eye to keep the latter 
in focus. 

Realising the unsatisfactory condition 
of affairs, Sir Frank Baines of the Office 
of Works, after giving very careful con- 
sideration to the subjects involved, 
referred to the National Physical 
Laboratory a design of a roof which 

Fig I cross Section through Model 
without Screen . 

should diminish to a very considerable 
extent the trouble due to reflections 
from the glazing. The main idea is to 
reduce as far as practicable the general 
lighting on the floor of the gallery, 
so that spectators will be illuminated 
as little as possible ; and yet to provide 
adequate illumination on the walls. 

The design is shown in Fig. 1, from 
which it is obvious that the result will 
be very different from that in many of 
the rooms at the National Gallery, which, 
while being quite suitable for pictures 
without protecting glass, allows so much 
light to fall on the floor and objects in the 
room as to cause inconvenience of the 
kind described. 

It is, of course, impossible to prevent 
reflection from pictures on the opposite 
wall ; and, short of using a dark curtain 
along the length of a gallery, the best 



a © 

° 3 

to o 

■g a 

a I 
2 * 





way to minimise the effect is to keep 
the picture frames and the wall decora- 
tions, especially those above the picture 
line, low in tone, preferably somewhat 
lower than the average tone of the 
pictures. The experiments which have 
been made on these two points indicate 
the great value of the help resulting 
from the application of this principle of 
" monotony " in reducing the obtrusive- 
ness of the inevitable reflections occurring 
in galleries hung with pictures on both 
sides. A design of the type illustrated 
in Fig. 1 obviously reduces very con- 
siderably the total amount of light 
entering the room, as compared with 
galleries of which the roof is nearly all 
glass. It was one of the chief aims of 
the investigation undertaken by the 
National Physical Laboratory to deter- 
mine whether, with this reduction, 
sufficient illumination would be obtained 
on the pictures under the daylight 
conditions common in London. 

The question of orientation was of first 
importance, and it was considered that 
the most likely use to which such a 
design might be put would be to a 
gallery running east and west. 

Gallery with Length East and West. 

In a gallery with length east and west 
it is necessary to keep the sun ofi the 
north wall. The N I'.L advised that the 
best way to prove any design qualitatively 
and quantitatively was to make pre- 
liminary experiments on a scale model. 
since illumination values would be 
independent of scale. They also 
suggested that direct sunlight should be 
kept off the north wall by a vertical 
screen of sufficient height, which should 
be highly reflecting on the north side, 
and so make use of light from the north 
part of the sky for illuminating the 
pictures on the north wall, light from 
the same quarter naturally being incident 
on the south wall. (Fig. 2.) In this 
way, by adjusting the height and position 
of the screen, the illumination on the 
north and south walls might be made 
sufficiently equal, so that no material 
difference between them would be noticed 
whether the sun were shining or not. 

A model was therefore built in the 
yard of the National Gallery to a one- 
third scale of a room 80 ft. by 40 ft. 

Experiments were made in various 
kinds of weather on the height and 
position of the screen and on the 
decoration of the walls. The quantity 
measured was the daylight factor, which, 
for the purpose of these experiments, 
was defined as the ratio of the illumina- 
tion on a small vertical part of the wall 
to the illumination on a horizontal 
area out of doors, shaded from direct 
sunlight. Similar illumination measure- 
ments were also made in a number of 
the rooms of the National Gallery. 


The general results were that a design 
on the lines proposed with a screen of a 
height suitable for preventing sunlight 
reaching the north wall, it was possible 
to equalise the illumination on the 
north and south walls, to have the walls 
decorated in a suitable low tone, and 
yet provide adequate illumination on 
the pictures. The general illumination 
on the floor of the room was reduced 
to about a quarter of that in some of 
the existing galleries. 

Gallery with Length North and South. 

The application of the general design 
is somewhat simpler in the case of a 
gallery with length east and west than 
in the case of one with its length north 
and south. Without any screens a 
north and south gallery would have the 
sun on the west and east walls in the 
morning and afternoon respectively, and 
for the whole day on parts of the north 
wall. For the purpose of experiments 



.■** ~ 

a "2 

a £ 



on methods of overcoming these 
difficulties the model was turned through 
an angle of 90° and transverse screens 
were fixed between the roof ridges 
(Fig. 3). Various distances between the 
Bcreens were tried, and they were hinged 
at the top so that the lower edges could 
be pulled towards the south. In this way 
a given area of screen is somewhat more 
economically used than when in the 
vertical position, and light from the north 
part of the sky is rather more used than 
that from the south part. The illumina- 
tion towards the south end of the gallery 
is thereby also made practically equal 
to that of the north end. The general 
results are very similar to those obtained 
with the model when its length was east 
and west. 

Fio 3 Cross Section through North-South Model 
with Screens . 

Circumstances have not yet permitted 
the construction of roofs on these lines 
to be undertaken. 

It is desired to acknowledge the great 
assistance of Messrs. Pitcher and Rose 
of H.M. Office of Works, in carrying out 
the construction, and the various 
modifications made in the model gallery. 


E. P. Hyde. The Lighting of Cleveland 
Museum of Art. Transactions Ilium. 
Eng. Soc, New York, Vol. XL, 1916, 
page 1,014. 

Studio and Art Gallery Lighting. 
Illuminating Engineer. Vol. VII., 1914, 
page 148. 

S. H. Seager. The Lighting of Picture 
Galleries and Museums. Journal of the 
Royal Institute of British Architects, 1912. 


The investigations carried out by the 
Photometric Department of the National 
Physical Laboratory, on behalf of the 
Office of Works, on the daylight and 
artificial illumination of buildings of 
various types used for many different 
purposes, have laboured under con- 
siderable disadvantages. The work has 
entailed much loss of time in travelling, 
and it has seldom been possible to make 
such variations in window arrangement, 
decoration and methods of illumination 
as have been desirable. There are so 
many different problems of importance, 
in which illumination is one of the 
governing factors in architectural design, 
that the Office of Works decided that an 
Illumination Laboratory would be well 
worth its cost. The design of the day- 
light illumination of buildings for instance 
has been in the past inevitably based on 
rough and empirical rules. 

There is, for instance, practically no 
data available for determining the change 
which should be made in a design found 
suitable for a building with a given 
orientation, in order to adapt it to a 
different orientation. The seasonal 
change of the daylight factor applicable 
in this country to different aspects has 
probably not been experimentally deter- 
mined. Other architectural problems in 
connection with daylight illumination 
awaiting more detailed investigation are 
measurements of diversity factor, on 
which to found recognised limits, the 
correlation of window height with width, 
and also spacing with width of room, 
the proportions of lighting areas, the 
height and design of skylights, questions 
of lateral lighting, the effect of neighbour- 
ing buildings in diminishing the effective 
illumination, and the measurement of 
reflection ratio of building materials. 
Other problems arise from the study of 
corridor fighting and measurements, of 
the effects of obscuring, and prismatic 

It is obvious that it is impossible to 
carry out much work of such a nature 
in ordinary buildings, which are required 
for use as offices or for other purposes. 
The effects of variation of dimensions or 
decoration under both natural and 



artificial lighting conditions cannot be 
properly studied in such circumstances. 

Realising that improvements in know- 
ledge on which design is founded may 
be expected to result in considerable and 
occasionally in great economy, as it is of 
the greatest importance, for instance, 
that valuable building sites should be 
develoj)ed to their utmost capacity, the 
Treasury have sanctioned expenditure 
on the construction of a building for 
carrying out illumination experiments. 

serious remains to be seen, and eventually 
it may be found desirable to enclose it 
completely. The ground is of concrete 
with a slight slope to the sides. Into it 
battens are dove-tailed, at 4-ft. centres 
in both directions, to which the models 
can be screwed down. Provision for 
the supply of electric power is also 
being made. 

The building will be large enough to 
permit of several models being tested 
together. The use of turn-tables will 

Fig. 1. — Showing new building for illumination experiments at National Physical 
Laboratory, in course of erection. 

It is expected that in most cases, 
especially for daylight measurements, 
scale models will suffice, so that the 
most convenient absolute size can be 
chosen. The building itself is merely a 
glass roof structure 60 ft. by 30 ft. by 
17 ft. to the gutters, supported on 10 in. 
by 7 in. stanchions. It is intended to 
build up the experimental models out 
of wood and canvas underneath it. In 
order to avoid expenditure which was 
not absolutely necessary, the work will 
be begun without filling in the vertical 
sides of the building with glass. Whether 
the disadvantage of not being entirely 
wind and weather proof will be very 

enable direct and definite figures to be 
obtained on such subjects as the relation 
of daylight and other factors to compass 

The building will be available for the 
experiments carried out on behalf of 
the general public, and it is hoped that 
it will prove not the least useful part 
of the plant of the Photometric Depart- 
ment of the Laboratory. 

(The discussion of this paper, together 
with Capt. W. J. Liberty's contribution 
on the Lighting of various Decorative 
Interiors, will appear in our next issue 




An interesting but simple method of fog- 
signalling was recently introduced on the 
Metropolitan Railway, and is now being 
generally used on the Underground Rail- 
ways of London. Formerly, as is well 
known, cautionary signals to drivers 
during fogs were given by means of 
detonators placed on the line, some 
distance before reaching the stop signals. 
The placing of such detonators on the 
line was effected automatically from a 
magazine containing a large number, 
which inserted the detonator on the line 
whenever the stop signal was against the 
on-coming train. The noise of the 
detonator warned the driver that the 
stop signal, which he could Dot 
owing to the fog, was against him, and 
enabled him to slow up in good time. 

Although the process was automatic, 
being worked by an electro-pneumatic 
arrangement controlled by the stop 
signal, it had drawbacks in that a fog- 
man had to be provided to look after 
several machines to see that the maga- 
zines were kept charged with detonators. 

The large number of detonators used 
makes the process comparatively cost 1 v. 
and the frequent explosions during a fog 
are apt to be considered a nuisance by 
passengers or persons residing near the 
railway. A much simpler and more 
economical device, now introduced, is 
the use of an electric lamp signal pro- 
vided with one orange and one green 
Fresnel concentrating lens, placed about 
five feet from the track at the point of 
warning. The beam of light is focused 
for a point at the motorman's eye-level 
when 50 feet away from repeater. 

The lighting main for these fog repeater 
signals is controlled by a switch in the 
signal cabin or nearest station and 
operated by the signalman or station 

We understand that the introduction 
of this simple device has brought about 
a considerable saving due to dispensing 
with fog-man and detonators, and that 
it has proved quite satisfactory in opera- 
tion, and during the recent dense fog the 
trains were only a few minutes behind 
schedule time. 

A committee has been appointed by the 
Medical Research Council to advise them 
upon the promotion of researches into 
the biological actions of light, with a 
view to obtaining better knowledge of 
the effect of sunlight and other forms of 
light upon the body in health or disease. 

The committee is constituted as 
follows : Professor Sir W. M. Bayliss, 
F.R.S. (Chairman), Mr. J. E. Barnard, Dr. 
H. H. Dale, F.R.S., Captain S. R. Douglas 
(late I.M.8.), Sir Henry Gauvain, M.D., 
Dr. Leonard Hill, F.R.S., and Dr. J. H. 
Sequeira, F.R.C.P. Dr. Edgar Schuster 
is Secretary. 

The Chairman, Prof. Sir W. M. Bayliss, 
who is a member of the Council of the 
Illuminating Engineering Society, will 
no doubt ask the committee to devote 
some of their time to the consideration 
of the action of light upon the eye. 


Mr. Geokc.e Herbert, in a paper read 
before the Rochdale Association of 
Engineers on January 20th, dealt with 
the subject of industrial illumination 
from the point of view of maximum 
output at minimum cost. The necessary 
requirements to produce correct and 
efficient illumination were pointed out. 
Satisfaction could not bo expected if these 
requirements were neglected. 

It was shown that from all standpoints 
good lighting was essential. Emphasis 
was placed upon the necessity of suitable 
reflectors to meet the special require- 
ments of the case under consideration. 
The chief consideration is the elimination 
of inconvenient shadows and glare. 

The position of the man who hopes to 
sell lighting was next considered. It 
was shown that if he wishes to satisfy 
his clients he must be in a position to 
talk " forcefully " and authoritatively 
upon the proved advantages of good 
illumination, i.e., to back up his state- 
ments by technical knowledge. 

In conclusion, Mr. Herbert urged all 
those interested in lighting to join the 
Illuminating Engineering Society, whence 
he had derived much of the data in his 



INDEX, April, 1922. 

Editorial. By L. Gaster 

Fog Signals on Railways, Electric Lamps as 

Jliuminatino JEnflineerina Society— 

(Founded in London, 1909) 
Account of Meeting on March 28th 
New Members 

The Lighting of Public Buildings ; Scientific Methods and Architectural 

An Account of Experimental Work and Results by E. H. Rayner, 
Sc.D., J. W. T. Walsh, M.A., M.Sc, and H. Buckley, 
B.Sc, of the National Physical Laboratory 

Industrial Lighting 

Light, Action of, on the Human Body 

Reviews of Books 

Topical and Industrial Section 






The Empire Municipal Directory and 
Year Book ( Published by the Proprietors 
of " Municipal Engineering and the 
Sanitary Record,'" 1922. pp. 288 + 16 
+vi., lis. post free in U.K.). 

The edition of this publication for the 
year 1922 — 23, the 40th year of issue, 
makes a welcome appearance. The usual 
complete list of corporations, County, 
Urban and Rural District Councils, both 
in this country and in the overseas 
Dominions, together with names of 
County and Municipal Engineers, Sur- 
veyors, etc., is provided. A list is also 
given of scientific societies, and other 
bodies concerned with public health. 

The series of articles dealing with 
various aspects of municipal engineering 
is again a useful feature. We notice that 
the section on Public Lighting has 
undergone considerable revision, reference 
being made to new types of lamps and 
reflectors, and some data on illuminating 
engineering added. There is a biblio- 
graphy of works- dealing with all aspects 
of public health and sanitary engineering, 
including lighting, heating and ventilation, 
and the volume terminates with the usual 

The directory should be of considerable 
value to engineers and others concerned 
with municipal engineering. 

Research in Industry. By A. P. M- 
Fleming, C.B.E., M.Sc, M.I.E.E., and 
J. G. Pearce, B.Sc. (Eng.) A.M.I.E.E. 
(Sir Isaac Pitman & Sons, Ltd., 
London, 1922. 10s. 6d. net. pp. 224 
+ 11). 
In this book, which forms one of Pitman's 
Industrial Administration Series, a useful 
summary is given of present tendencies 
in industrial research, with which the 
names of the authors are prominently 
identified. The introductory chapters 
contain an analysis of research and existing 
agencies for its development, and a study 
of its influence on industry. The 
authors then proceed to a discussion of 
co-operative industrial research, works 
research organisations, and the design 
and equipment of research buildings. 
The latter chapter is illustrated by 
pictures of a number of famous research 
institutions and laboratories. The final 
chapter deals with international aspects of 
research, many forms of which should 
receive attention in all countries in the 
common cause of humanity. There is a 
most useful bibliography and an adequate 

In the space available we can give only 
a brief indication of the contents of this 
work, but it well repays study, and we 
are in cordial agreement with the author's 
statement that the need for highly 
organised industrial research was never 
greater than it is to-day. 




[The contents of these pages, in which is included information supplied by the makers, will, 
it is hoped, serve as a guide to recent commercial developments, and we welcome the receipt of all 
bona-fide information relating thereto.] 


The new 

B.T.-H. "Trutint 
matching Unit. 


The accompanying illustrations will give 
an idea of two tonus of B.T.-H. 
" Trutint " units for colour inatcliing. 
One form consists simply of a reflector 
and screen, contained in a metal ring 
secured by thumb-screws to the reflector. 
This form is for pendant use in industrial 

special glass correcting screen is the 
result of very careful research and that 
a very close resemblance to normal 
daylight is obtained. As readers are 
aware from previous notes in this Journal, 
artificial daylight is now receiving much 
attention and has proved of great value 
in such processes as dyeing, paint and 

Fig. 1. — B.T.-H. "Trutint" 
Unit for pendant use, show- 
ing special daylight glass 
screen detached from re- 

and commercial establishments, and is 
supplied in three sizes for 100, 200 and 
500 watt Mazda gas-filled lamps. The 
other unit is made in one size only, for 
100 watt lamps, and the reflector and 
screen are fitted to a standard with a 
switch in the base, suitable for use on 
counters, desks, etc., to produce local 
" artificial daylight." 

We are informed that the choice of the 

Fig. 2.— B.T.-H. " Trutint " Unit 
standard type for use on 
counters and tables. This unit 
is finished in antique copper 
and has a switch in base. 

chemical examination, colour printing, 
and the grading by colour of leather, 
cotton, tobacco, seeds, etc. In addition 
it has opportunities in museums, art 
studios, picture galleries, etc., and other 
places where correct appearance of 
colours is important. 






illuminating EnoineeriuQ Societp. 

(Pounded in London, 1909.) 


Tel. No. Victoria 5215. 


The Lighting of Decorative Interiors. 

In the course of the discussion on " The Lighting of Public Buildings," 
which took place at the meeting of the Illuminating Engineering Society 
on March 28th and is dealt with in this issue, a series of photographs, 
recently taken by the actual artificial light of the installations and illustrat- 
ing methods of illumination in interiors of architectural distinction and 
historic interest, were shown by Capt. W. J. Liberty. Lighting installa- 
tions of this kind raise many questions of interest alike to illuminating 
engineers and architects. We have, first, interiors in which fittings and 
chandeliers of historic interest are retained but adapted in due course to 
modern illuminants, of which the Guildhall is doubtless a typical example. 
One sometimes encounters a desire to retain such chandeliers, even when 
they are not in themselves well adapted to modern methods of lighting. 
The best one can do in most circumstances is to try to effect the conversion 
with as much artistic skill as possible and to render the lamps installed 
unobtrusive. One of the most important points is the avoidance of glaring 
exposed filaments and the use of suitable reflectors whereby better dis- 
tribution of light is secured. 

We have, next, the case of an ancient interior where no chandeliers or 
other appliances exist, and where the expert has a free hand, subject to his 


preserving the spirit of the building and avoiding the introduction of such 
modern lighting fittings as are clearly incongruous. In the discussion before 
the Illuminating Engineering Society the simple lighting fittings installed 
in the Crypt at the Guildhall were considered appropriate. Here again 
the shielding of brilliant sources is a vital point. 

Finally, we have the case of a modern interior which may or may not 
conform to some traditional style of decoration, and where both utilitarian 
and aesthetic considerations require consideration. 

Such questions involve the wider problem whether in modern buildings 
one should seek to perpetuate the traditional decorative schemes of the 
past, or whether one should aim at something new ? In a recent Con- 
ference on Lighting of the Design and Industries' Association, it was frankly 
recognised that the use of modern methods of lighting necessarily involves 
a departure from precedent ; and that the design of fittings, while subject 
to artistic craftsmanship, should be developed in such a way as to enable 
these illuminants to be used to the best advantage. Otherwise some 
sacrifice of efficiency and utilitarian value is inevitable. 

We have now come to a new period, namely, the age of electric lighting, 
and the older illuminant, gas, is likewise being developed in an enterprising 
way to meet modern requirements. It seems likely that in days to come 
people will look back with wonder at the present practice of so often 
attempting to apply these illuminants with obsolete fittings developed 
to meet quite different conditions. We are learning to adapt fixtures to 
modern needs, and to realise that they should be products of the twentieth 
century, not merely adaptations from the sixteenth or seventeenth centuries. 
The question was aptly summarised editorially in a recent issue of the 
Electrical World by the remark : ' ' The real problem is not how the 
Renaissance artists used candles, but how Cellini or da Vinci would have 
treated a single source of a thousand candles to the glory of his art." 

Many things which may be preferred from the purely decorative side 
are unfavourable to efficient illumination. It may be questioned, for 
example, whether the use of large crystal chandeliers in conjunction with 
electric gasfilled lamps is desirable in modem interiors ; whether the use 
of very dark wood panelling, which occasions much loss of light and is 
unfavourable to diffusion, should be widely used in other than purely 
decorative rooms. A great contrast to the effect of such sombre styles of 
decoration is presented by the main office at the new Port of London 
building, with its vast white dome and the massed gasfilled lamps therein. 
The absence of large pendant chandeliers in so large an interior is an 
interesting departure, and the room, when completed, should deserve study. 

From the information obtainable, one draws the gratifying inference 
that conditions of illumination in public buildings are now receiving much 
more attention than in the past. The account given by Mr. Chas. Baker, 
of the new Middlesex Sessions building, where decorative and utilitarian 
aspects seem to have been very happily blended, confirms this belief. In 
public buildings decorative aspects should receive special attention. Yet, 
as the rooms are put to useful purpose, being in fact devoted to administra- 
tive and clerical work, -utilitarian considerations must also be studied. 
In such cases the co-operation of architects and lighting experts is par- 
ticularly desirable, and no doubt in the future opportunities will be given 
for a more detailed study of these problems at the hands of the Illuminating 
Engineering Society and the Royal Institute of British Architects. 


Ancient Light Cases and Photometric Measurements of Daylight. 

In our last issue, in referring to the new experimental building erected 
in the grounds of the National Physical Laboratory, and described in the 
Paper read before the Society on March 28th by Messrs. Rayner, Walsh 
and Buckley, we remarked on the value of scientific predeterminations of 
daylight in buildings. That photometry is of great aid in the study of 
daylight conditions, as well as artificial illumination, is now well recognised. 
The method of relating the total unrestricted outdoor illumination to the 
actual illumination at some point in a room, by means of the "daylight 
factor " or the " sill ratio," was used with good effect in the researches of 
the Joint Committee of the Society on the natural lighting of schools,* and 
again in the researches conducted by the Home Office Departmental Com- 
mittee on Lighting in Factories and Workshops. It has also been applied 
very usefully by Mr. P. J. Waldram and others to ancient light cases, in 
which the effect of some adjacent obstruction on the access of daylight 
into a building is under dispute. 

On pp. 152-153 in this issue we deal with a very interesting case of 
this kind that recently arose in Bradford, where an injunction was applied 
for to restrain the Bradford Corporation from erecting an electric light 
station on the ground that it would cause an obstruction to the light of 
the windows of the premises of the plaintiffs (Messrs. Chas. Semons & Co., 
Ltd.). The judgment of Mr. Justice Eve, who tried the case, is of great 
interest. The issue, he decided, was whether the erection would render 
the plaintiffs' premises " substantially less convenient for beneficial use 
and occupation for the purposes of the plaintiffs' business." In giving 
judgment in favour of the defendants he quoted the evidence of Mr. P. J. 
Waldram, to whose impartiality and lucidity he referred in complimentary 
terms, and whose photometric measurements of daylight proved very 
useful. He referred also to the absence of any satisfactory practical tests 
on behalf of the plaintiffs. 

It is not so long since the production of photometric measurements 
in a court of law would have been attended with difficulty and possibly 
would have carried little legal weight. The position is now very different, 
and the value of scientific tests of daylight in deciding such cases has been 
amply vindicated. Mr. Waldram, as our readers are aware, has made a 
special study of these measurements and dealt with them at various 
meetings of the Illuminating Engineering Society. It is mainly through 
the Society's educational work that they are now better appreciated. 

There is, however, a great deal of work still to be done in this field. 
In particular, researches are needed to determine what reduction in light 
will have an actual prejudicial influence in the manner Mr. Justice Eve 
mentioned. It is clear that there is no prescriptive right to unrestricted 
daylight, but only to daylight which is sufficient in the sense indicated. 
Records of actual performance of work, supplemented by photometric 
tests, would prove useful in determining the limiting value of illumination 
below which supplementary artificial light becomes necessary. But the 
co-operation of the ophthalmic surgeon is also necessary in order to decide 
how far natural illumination can be diminished before the requirements 
of the normal eye cease to be met, and there is accordingly fatigue of vision. 
The whole subject is of great importance to the architect, who should 
find the experience of the Illuminating Engineering Society in this field 
of work of considerable value. 

* Illum. Eng., August, 1913. 


The Circle of Scientific, Technical and Trade Journalists. 

The Scientific Trade and Technical Circle of the Institute of Journalists 
has done a great deal of useful educational work, and readers will find in 
past issues of our Journal many references to their discussions and visits 
to educational institutions, etc. During the latter period of the war its 
activities unavoidably fell into abeyance, owing to the many special dem ands 
on the time of members, but it is recognised that the moment is opportune 
for a revival. 

Accordingly an informal gathering was arranged on May 30th, at the 
Hall of ' j Institute of Journalists, at which the writer presided. After 
member- ' id dined together, a discussion ensued on the future of the 
Circle, ar;^ it was agreed that the time was ripe for the resumption of its 
full activities. Accordingly a small committee was appointed to take 
advantagi ' ny opportunities that arise for discussions and visits during 
coming m _£ Jis, and to prepare the ground for a general meeting to be 
held ne? t |£ ember, when new officers will be elected and the programme 
for the ->sion presented. An interesting discussion was initiated by 

Mr. Perc .. Marks on the duties of Secretaries and their relation to the 
trade and echnical Press. 

A poin; of great importance, raised by Mr. Sewell, was the question of 
postal rates, which has recently been dealt with by the Institute of 
Journalists. The plea that concessions would occasion loss of revenue to 
the Post Office only takes into consideration one narrow aspect of the 
matter. The present high postal rates are responsible for various economic 
losses to the country, in addition to the very prejudicial restricting effect 
that they exercise on the dissemination of useful information. We have 
frequently drawn attention to the anomalous position of many technical 
journals and transactions of scientific societies, which constitute one of 
the most valuable educational forces in this country and deserve every 
encouragement, and we also think that publications concerned in the 
promotion of British trade should be treated on a more liberal basis. 

Another question of immediate interest is the treatment of scientific 
and technical matters in the Press. Reported " discoveries," for which 
great claims are made, should be carefully scrutinised by experts before 
being given wide publicity. Preliminary consultation with technical 
journalists would often prevent injudicious support of claims that after- 
wards prove to be ill-founded. The Circle, being composed of journalists 
with knowledge of many different technical subjects, should act as a link 
between science and journalism, to which the Press could turn for guidance. 
The wide influence of the Press, used with discrimination, should be of great 
assistance to the advancement of science, and we gladly take this oppor- 
tunity of acknowledging the very valuable publicity given, both by the 
technical and daily Press, to the aims of the Illuminating Engineering 
Society. It would add greatly to the prestige of journals if it were recognised 
that their comments were always based on first-hand expert information. 

Leon Gaster. 





She 3Uuminatino Engineering Society 

(Founded in London, 1909.) 

The Illuminating Engineering Society is not, as a body, responsible 
for the opinions expressed by individual authors or speakers. 


Joint Discussion with the Royal Institute of British Architects. 

(Proceedings at the meeting of the Society held at the House of the Royal Society of Arts, 
18, John Street, Adelphi, London, W.C., at 8 p.m., on Tuesday, March 28th, 1922.) 

{Continued from page 127 in April issue.) 

Following the reading of the Paper bv 
Messrs. E. H. Rayner, J. W. T. Walsh and 
H. Buckley, Capt. W. J. Liberty pre- 
sented some beautiful pictures, illus- 
trating the lighting of public buildings of 
architectural distinction and historic in- 
terest, The photographs had been taken 
by the Hon. Asst. Secretary of the 
Society, Mr. J. S. Dow. Capt. Liberty, 
from his intimate acquaintance with 
such buildings, remarked that the pictures 
were interesting as showing how decora- 
tive features required special treatment. 
The special problems involved could only 
be met by using appropriate fittings, and 
there were other circumstances to consider 
besides the provision of a certain illumina- 
tion in foot-candles. Amongst such con- 
siderations light and shade were of 
importance. In a number of cases the 
special effects of shadow made it necessary 
to depart from conventional methods ; in 
others history and tradition demanded a 
departure from the methods pursued on 
purely utilitarian grounds, and the use of 
lighting furniture such as might not be 
selected from a strictly technical aspect. 
Capt. Liberty pointed out that in recent 
years there had been a steady increase in 
the amount of light considered necessary. 

In modern buildings, such as are now 
being erected for business and adminis- 
trative purposes, 3 foot-candles was a 
usual and quite feasible value, which in 
many cases was exceeded. 

The first illustrations shown related to 
the Guildhall. The Council Chamber 
(Fig. 1) was lighted by a large chandelier, 
mounted in a high dome and necessarily 
out of view in the photo. This was 
studded with incandescent lamps, and 
the same method was followed in the case 
of the two standards on either side of the 
chairman's desk, visible in the picture. 
These fittings, though probably not such 
as would now be selected for a new build- 
ing, were of historic interest. The general 
illumination was approximately li foot- 

In the adjacent Court of Aldermen the 
illumination was furnished by more 
modern methods, namely, by two pen- 
dants equipped with gasfilled lamps in 
opal glass bulbs, equipped with Holophane 
reflectors. The effect was soft and 
pleasing, and a considerably higher 
illumination; amounting to' 4 foot-candles, 
was provided. 

The third illustration showed the 
lighting of the Crypt at the eastern end 



%• . V» 


l-'ii.. 1. — Vii'w i if Cduncil Chamber Guildhall. 

Fig. 2.— Showing lighting of Crypt at eastern end of Guildhall, lighted in a simple 
but appropriate manner. 



of the Guildhall. This Crypt was of very 
great historic interest and contained 
some interesting remains and relics, 
having withstood the Great Fire of 1666. 
The simple but effective method of light- 
ing was in keeping with the nature of the 
interior. The gasfilled lamps were 
screened with panes of frosted glass, the. 
interior reflectors being silvered, the whole 
giving a soft effect and conveying the idea 
of primitive simplicity. 

As an example of the combination of 
old and modern methods Capt. Liberty 
also showed a photograph of the Dyer's 
Hall, which has already been reproduced 

mission had been granted for a few 
photos to be taken. The first of these 
showed typical semi-indirect lighting in a 
corridor. The second view was taken in 
the vast main office, which was not only 
of great interest architecturally, but in- 
volved most interesting lighting prob- 
lems. The chief feature was the very 
large central dome, decorated in white, 
within which gasfilled lamps aggregating 
20,000 candlepower were installed. The 
diameter of the room at floor level was 
110 feet between the piers behind the 
40 columns. The diameter of the floor 

Fig. 3. 

-Typical Corridor in new Port of 
London Building. 

Fig. 4. — Main Office in Port of London Building. 

in this journal. The main lighting was 
effected by indirect electric lighting, 
showing up the highly decorative ceiling, 
and supplemented by wax candles placed 
on the table. 

The foregoing buildings were of some 
antiquity. Capt. Liberty then referred 
to the Port of London Building, as an 
instance of a new building in the City of 
London where modern methods of light- 
ing were being installed. He hoped in 
the future, to give a more detailed account 
of the lighting of this important building, 
the decoration of which was in course of 
completion. Meantime, by the com 
of Mr. Edwin Cooper, the architect, per- 

level of the Dome of St. Paul's Cathedral, 
he stated, was 96 feet. The view was 
taken from the top of scaffolding some 
30 feet high. The decorative white sur- 
face used in this room was conducive to 
excellent diffusion of light, and the in- 
terior appeared brightly illuminated. 
Amongst other problems he might men- 
tion that the position of the lights within 
the dome had been the subject of much 
study, with a view to obtaining the best 
shadow effects on decorations round the. 
edge of the dome. He understood that 
it was proposed to supplement the central 
lighting by local lamps placed between 
the pillars, opposite the medallions 



immediately below the edge of the dome. 
He had no doubt that, when completed, this 
would prove a most striking installation. 
Another recently erected building for 
which Mr. Cooper was responsible was 
the Marylebone Town Hall. This also 
furnished some interesting examples of 
lighting. The first view showed the light- 
ing of a landing immediately above the 
main steps, where there was a war 
memorial. Light was furnished by a 
bowl fitting mounted direct on the ceiling, 
the tip of which could just be seen in the 
illustration. The concealed lighting of 
the memorial was effective, and attention 
might also be drawn to the pedestal lights 
on either side of the Btairway. 

Fig. .">. Showing concealed lighting of Landing 
and War Memorial at Marylebone Town Hall. 

A very charming view was presented 

in the next illustration, which showed a 
corridor leading to the vestibule outside 
the Council Chamber. Through the open 
door the chairman's seat could be seen, 
and there was a clear view down the 
corridor. The light was furnished by 
eight lights mounted in a small dome, the 
illuminated interior of which was just 
visible in the photograph. The Council 
Chamber itself was panelled in elaborately 
carved walnut and lighted by two crystal 
chandeliers, supplemented by bracket 
lights. The interior of the crystal 
chandelier was furnished with gasfilled 
lamps, and electric candles were arranged 
round its edge. The contrast be ween 

the bright chandeliers and the very dark 
panelling made it a difficult subject to 
photograph, and from the illuminating 
engineer's standpoint the choice of such a 
dark lining for the walls,, which reflected 
relatively Little light, was a point for 
discussion. The same applied to an 
adjacent Committee Room, where similar 
dark panelling was used, but indirect 
cornice lighting was provided. He would 
like to hear the views of those present as 
to the advisability of having very dark 
walls with a brightly illuminated ceiling. 
It was. he thought, recognised that this 
tended to accentuate the height of the 
room. He understood that tin* illumina- 
tion on the desks and tables in these 
rooms was of the order of 2| foot-candles. 

('apt. Liberty added that, by the 
courtesy of Mr. ('lias. Baker, Electrical 
Engineer to the L.C.C., he and Mr. Dow- 
had visited two new buildings — the 
Middlesex Sessions and the L.C.C. Hall 
on the Embankment. The former was an 
excellent example of modern methods of 
lighting. The walls and furniture were 
mainly of light oak, and Bemi-indirect 
lig hting was very generally employed. 
The Bemi-indirect fittings installed in the 
domes in the three courts had a particu- 
larly pleasing effect ; and the lighting of 
the entrance hall, where the illumination 
was afforded entirely by lamps in diffusing 
globes mounted on ornamental brackets, 
had interesting features. One received 
the impression that the Lighting through- 
out the building was amply adequate, 
and it seemed to be an excellent example 
of modein methods. 

Regarding the County Hall on the 
Embankment, not much could be said as 
vet, as the building was still being com- 
pleted and the Lighting arrangements 
were not very far advanced. It was 
evident, however, that it would contain 
many interesting examples of lighting, 
to which he would like to refer on a future 
occasion. One feature he might mention 
was the great length of the corridors 
throughout the building. 

Mr. E. A. Llewellyn (H.M. Office of 
Works) in opening the discussion ex- 
pressed his appreciation of the Paper. 
Generally, lie considered that semi-in- 
direct lighting gave better diffusion ami 
approximated more closely to daylight 
than any other system, and was for those 



reasons preferable. He emphasised the 
need for the compilation of further and 
better data in regard to daylight lighting, 
as this consideration affected very ma- 
terially the design and cost of all build - 

ascertain what height of room would give 
daylight illumination in the centre of all 
floors which would be adequate for the 
assembling of small and intricate work. 
He considered that the series of photo- 

Fig. (i. — A Charming example of concealed lighting in the corridor leading to the Council 
Chamber at Maiylebone Town Hall. 

ings, perhaps more especially of factories 
and industrial premises. He instanced 
the problem of a building of several 
storeys high and 70 feet wide, side Lig 
by windows equal to 30 per cent, of th< 
floor area, in which it was necessary to 

graphs shown by ('apt. Liberty was most 
instructive to the architect, particularly 
those, illustrating the external lighting of 

buildings at night. This was a subject 
which merited more attention than it 
received at present in this country. The 



view of the Capitol at Washington, flood- 
lighted from concealed sources, was most 
impressive. One contrasted it with a 
view of St. Pauls Cathedral on a winter 
evening — a drab, indistinguishable mass. 
The flood-lighting of St. Paul's and other 
buildings of which we are justly proud, 
would go far to make London and our 
great provincial cities brighter and more 
interesting at night. 

Mr. P. J. Wai.dkam said that he con- 
sidered the paper of very great interest, 
both to architects and illuminating en- 
gineers. Information on the effect of 
reflection from walls and ceilings was 
particularly needed. Given sufficient 
data he saw no reason why " utilisation 
factors " for daylight should not be set 
up in order that any desired standard of 
natural illumination might be obtained 
with the same precision that standards of 
artificial illumination can be. obtained for 
specified conditions. He recalled that 
the Transactions of the American Illumin- 
ating Engineering Society of 1911 con- 
tained some useful researches on the 
effects of various coloursof wallpapers and 
ceilings. It was desirable not to over- 
emphasise the value of measurements of 
illumination, important as they doubtless 
were. Values so obtained must be in- 
terpreted with due regard to the sub- 
conscious effects on the observer, and it 
was in this field that the experience of the 
architect should he particularly helpful. 

Major H. C. Gunton (Post Office Eng. 
Dept.) expressed his appreciation of the 
Paper. He though.1 t hat the Society was 
doing most useful work in bringing archi- 
tects and illuminating engineers together 
in a joint discussion on the subject. A 
stage had now been reached where co- 
operation was more valuable than ever, 
especially in regard to avoidance of 
lighting conditions liable to cause eye- 
si rain. 

In the G.P.O. they had passed through 
all stages of illumination, from the carbon 
filament to metal filament lamps, and 
more recently to indirect or semi-indirect 
methods of gasfilled lamps. It was 
generally agreed that semi-indirect light- 
ing gave a more cheerful effect than in- 
direct methods, and they were disposed 
to favour semi-indirect methods for this 

reason. Co-operation between architects 
and engineers was also of value in view 
of its influence on maintenance. Installa- 
tions should not be designed solely with 
a view to initial effect without due con- 
sideration for possible depreciation. In 
practice it was necessary to allow for this, 
and it was usual to provide for adequate 
illumination throughout the period before 
redecoration is necessary. Depreciation 
included not only drop in candlepower of 
lamps but diminution in reflecting power 
of surroundings. The scheme of decora- 
tion selected had a vital influence on the 
conditions of lighting, and light-tinted 
surfaces were much to be preferred. 

Another surface to be considered was 
that of the paper illuminated anil the 
colour of the ink used in writing upon it. 

During the past fifteen years they had 
prepared tables giving the standard of 
illumination requisite for various pur- 
poses. Tin- standard had risen materially 
during recent years. Values of illumina- 
tion were subsequently verified by tests 
with the lumeter. 

Mr. Chas. A. Baker (Electrical En- 
gineer to the L.C.C.) described the lighting 
of the Newington Session Court to which 
Capt. Liberty had referred. Most of the 
rooms were panelled in light oak, which 
gave — under artificial illumination — quite 
a bright and cheerful effect, but did not 
appear to advantage in a photograph. 
The Building presented a good example 
of modern methods of lighting, semi-in- 
direct, augmented by direct, lighting 
being very generally employed. The 
illumination in each of the courts was 
derived mainly from a semi-indirect unit, 
placed in the central dome : the result 
was particularly successful. Generally 
speaking, an illumination of 5 foot- 
candles was aimed at and obtained. 
The entrance hall was lighted entirely 
from side lamps, and there w r ere no 
pendant fixtures. On coming into the 
hall one received the impression of 
brilliant illumination, resembling that 
customary in the hall of a picture palace. 

He was interested to note that the 
authors were determining the best 
methods of lighting experimentally; to 
predict the result of semi-indirect illu- 
mination by calculation proved very 
difficult in practice. Various formula? to 



Fig. 7. — Showing lighting of Council Chamber, Marylebone Town Hall, by crystal 
chandeliers and bracket lights. 

Fig. 8. — Showing illumination of Comi ttee Room. Marylebone Town Hall, b}- 

indirect cornice lighting. 

I \2 


calculate the illumination derived from 
indirect lighting had been proposed ; they 
were com plicated and contained so many 
unknown factors, that he found in 
practice the best method was to put up 
typical units in a room and ascertain the 
illumination derived with a lumeter. 

Personally he had no use for totally 
indirect lighting, but found semi-indirect 
lighting was exceedingly useful. The 
absorption of the bowls should be care- 
fully determined. One must use a 
variety of glass dense enough to prevent 
the actual filament being visible, and yet 
not too dense. Some recent examples 
submitted for testing had an absorption 
of only 6 per cent. He considered that 
the intensities to be aimed at for public 
offices was about 4 to 5 foot-candles. In 
corridors a rather lower illumination was 
sufficient; in fact, it was preferable to 
gel the effect, on entering an office from 
the corridor, of stepping into an area of 
brighter illumination. 

Mr. (J. Campbell remarked that in the 
Paper the 100 watt gasfilled lamps were 
assumed to give 10 lumens per watt, as 
compared with 12 lumens per watt given 
by manufacturers. There seemed much 
uncertainty regarding values of efficiency 
and the sooner a definite understanding 
was arrived at the better. 

In semi-indirect Lighting the matter was 
complicated by the fact that besides the 
efficiency of the lamp one had to consider 
the absorption of light by the bowls, 
which was very variable. It was common 
knowledge that opal bowls, even those 
] (resumed to be of the same type, differed 
considerably. Not only might the thick- 
ness of glass vary, but the density of the 
glass was not always identical. Further- 
more, the distribution of light from any 
semi-indirect fitting naturally depended 
on the exact position of the filament in 
the bowl, and to some degree, on the 
arrangement and construction of the 
filament in the lamp. 

He showed on the screen the photo- 
metric distribution curve of a 14 inch 
diameter cased glass opal bowl fitting 
with 150 watt (rated) actually 160 watt 
gasfilled lamp. 

From the polar curve it could be seen 
that the maximum intensity of 244 

apparent candlepower occurred at the 
144° and 155° zones. 

The minimum intensity at 0° was 
93 - 8 apparent candlepower. 

Lumen efficiency taken as a percentage 
of clear lamp : — 

In zone to 90° =2335 per cent. 
90 to 180° =60-85 „ 
to 180° =84-2 

These represented practical results that 
could be obtained from a commercial 
fitting of the best quality of this type of 

The question of deterioration in illu- 
mination owing to deposits of dust was 
a very important one in semi-indirect 
lighting. Regular and proper cleaning of 
lamps, reflectors and bowls should always 
be provided. 

Mr. Haydn T. Harrison congratulated 

the Society on having heard such an in- 
teresting Paper, which, like all those 
emanating from the National Physical 
Laboratory, was full of valuable data 
obtained by direct measurement. This 
data nearly all applied to the indirect or 
semi-indirect system of lighting ; he 
hoped that the authors at some early date 
would be persuaded to read some similar 
Paper on the direct system, or any system 
where such a doubtful factor as the re- 
flecting value of a ceiling was not used. 

An interesting feature of the Paper were 
the figures relating to the efficiency of 
the gasfilled type of lamps ; from them 
it was obvious that no gain in efficiency 
must be expected when using the smaller 
power lamps, especially as the high 
intrinsic brilliancy of the lamps made it 
essential that the direct rays be shaded 
from the eyes which often means a 
further loss of efficiency. 

It would therefore appear that the use 
of more powerful lighting units would 
become general, in order to obtain the 
advantage to be gained by the higher 
efficiency of the larger gasfilled lamp. 
This would mean reduced first cost of 
instalment, but would necessitate much 
greater care being taken in arranging the 
position of the units and the choice of 
type. Mr. Baker had referred to the 
absorption of light by opal bowls. He 
(Mr. Harrison) never hoped to get only 
6 per cent, absorption, as he found the 



loss through clear commercial glass 
averaged 5 per cent. In practice 11 per 
cent, loss was about the lowest for opal or 
similar glass, and that only when specially 
manufactured ; it was also well to 
remember that these figures related to 
the net loss after the reflecting value of 
the glass had been credited, many types 
of commercial glass transmitted only 
40 per cent., reflecting 40 per cent.; if 

reflecting surfaces, and at tin 1 same time 
diffuses the light to a comfortable degree 
of intrinsic brilliance. 

Capt. E. Stroud said that the authors 
were to be congratulated on the ex- 
ceptional opportunity in carrying out 
such exhaustive tests for office lighting, 
and the Society had gained a tre- 
mendous amount of technical data in 

the 40 per cent, reflected was absorbed 
by the ceiling owing to dirt or other 
reasons the semi-indirect lighting system 
became very inefficient. For this reason 
Mr. Harrison advocated the use of totally 
enclosing fittings, such as two hemispheres 
the upper of which had a high reflecting 
value and low transmission value, the 
lower a high transmission value ; this 
eliminated the bright patch of light on the 
ceiling, which occurs with semi-indirect 
lighting, excluded dust from the interior 

their placing the matter before them in 
such a comprehensive manner. It was 
to be hoped they would be able to con- 
tinue their tests with other methods of 
illumination, so that we might have data 
for comparative purposes. The paper 
mentioned that the tests were taken at 
the request of the Office of Works ; there- 
fore they were limited to some extent 
in the application. 

If he might venture to criticise the 
Paper, he would like to draw attention to 



the second paragraph, wherein it was 
Btated : "" The Bemi-indirect, which was 
considered to be the best method of 
lighting such rooms was adopted in the 
experiments." It would seem that the 
crux of the whole test rested in this 
sentence, insomuch that one would like 
to know why the Bemi-indirect method 
was considered to be the best. When one 
considered, first of all, the comparative 
inefficiency of the method adopted, and 
secondly, the depreciation due to gradual 
deterioration of decorationson which open 
bowl semi-indirect installations depend, 
one wondered why totally enclosed 
direct lighting by means of reflecting and 
diffusing glassware was not tested. Obvi- 
ously, the efficiency of open howl semi- 
indirect units depended firstly on the 
cleanliness of the inner surface, of the 
bowl and the lamp, and secondly on the 
reflective, co-efficient of the secondary 
source, the ceiling. 

With the tests that are lunch in the 
Taper, he. assumed that the decorations 
and units were clean. It would be in- 
teresting to know whether any tests were 
taken on the depreciation of the installa- 
tions after time periods. 

He noticed that in one installation 
adopted there was a diversity factor 
(ratio of maximum to minimum illumina- 
tion) of 21 : I. The maximum illumina- 
tion was 5 - 5 foot -candles and the mini- 
mum 2-2. This was a most interesting 
reading, as he would have thought it 
impossible, with such a semi-indirect in- 
stallation, to obtain Buch a large diversity 
factor. It would rather seem as though 
the uneven illumination was due to 
directly transmitted light. 

In conclusion, he wished to thank the 
authors for the extremely interesting 
Paper, and hoped that further tests would 
be forthcoming, which will help greatly 
in present every-day lighting problems. 

Mr. A. Cunnington said that the 
Paper rather gave the impression that 
semi-indirect lighting was the only 
modern method. Frequently he had 
found, when dealing with railway offices, 
that a combination of semi-indirect light- 
ing for general purposes and local lighting 
for desks was the best solution to give the 
necessary intensities for bookwork, with 
due regard to economy. 

A further advantage of the local light, 
especially if provided by means of a 
swivel bracket and fitted with a switch 
on the lampholder, was that it gave the 
individual just the amount of light he 
required where, and when it was needed. 
In large offices there would generallv be 
dark corners requiring more than the 
average amount of artificial light, and 
there would certainly he some clerks re- 
quiring a higher intensity of illumination 
than the normal. Local lighting allowed 
for these variable quantities. 

An extreme case of this kind might be 
seen in the beautiful central hall of the 
Port of London Authority, of which 
photographs had been shown. It would 
prove expensive in energy to light such 
an extensive interior entirelv bv a central 

Emergency flood-lighting of the new Memorial 

Arch al Waterloo Station. 

source, if it were found necessary to have 
20,000 candlepoWer of lamps burning for 
the sake of a few clerks working overtime. 

He referred also to the efficiency of 
lamps, and stated that in view of the 
relative inefficiency of the smaller sizes 
(such as 100 watts, which the authors give 
as 126 watts per candle) and their com- 
paratively short life, he had recently 
intended to install the ordinary 100 watt 
vacuum type, but on inquiry being made 
he found that they could not be obtained, 
or if they had been supplied the price 
would be the same as the gasfilled type. 

Mr. Cunnington also exhibited one or 
two slides, showing the effect of the flood- 
lighting of the new Memorial Arch at 
Waterloo Station. There was some diffi- 
culty in finding a suitable spot from 
which to project the light, but eventually 



two special diffusive searchlights of 
1,600 candlepower each were placed on 
granite pedestals, later to be occupied by 
ornamental lanterns. From these points 
the greater part of the light was dis- 
tributed, two small supplementary pro- 
jectors being used higher up on each side. 
The projectors were supplied by Major 
Ashley Waller, representing Messrs. 
Barbier, Benard & Turenne, a firm who 
specialise in lamps for searchlights, light- 
houses, &c. 

Mr. A. G. Ramsey (Engineering 
Division, H.M. Office of Works) 
(communicated) : — 

Ministry of Pensions, Acton — Capital 
cost and running charges of the 
Electric Lighting of large rooms, 
167 feet long by 37 feet 6 inches 


The tests which the National Physical 
Laboratory carried out at Acton enabled 
very considerable economies to be effected 
in the lighting installation. In the pre- 
liminary scheme prepared by H.M. 
Office of Works, an average utilisation 
coefficient based on approximate data 

relating to manufacturers semi-indirect 
fittings with opal glass bowls was adopted, 
and no doubt a satisfactory scheme would 
have resulted, but as very little accurate 
information had been published on semi- 
indirect fittings it was thought desirable 
to obtain really accurate data before 
deciding on a definite scheme for so large 
a building. 

The results of the experiments enabled 
my Department to reduce the proposed 
number of lighting points by over 400, to 
save over £1,000 on the installation cost, 
and to reduce the annual costs for 
maintenance and electric supply by 
approximately £270 and £100 respectively. 

In settling the scheme for the illumina- 
tion of large rooms occupied by massed 
staffs, it is of the utmost importance to 
design the installation so that adequate 
illumination be obtained for any reason- 
able arrangement of desks and to guard 
against unsatisfactory lighting should 
t he desks be rearranged at a future date. 

The spacing of the lighting points in 
the scheme as actually installed differ 
slightly from the test installation (No. 11), 
in that the figure of 7 feet 9 inches 

Table 1. — Initial 

Cost and Energy Consumption per Room. 

No. of 

Cost of Fitting 
and Lamp. 

Total cost per Total cost pet- 
point, room. 

Watts per 

Total units per 


19s. Id. 

£3 4s. Id. £83 6s. 2d. 



Cost of wiring-up to and including lanrpholder, £2 5s. Hours of burning, 600 per annum. 
Table 2. — Annual Running Costs per Room. 

Interest at 5 per 
cent, on installa- 
tion cost. 

Cost of current at 
5d. per unit. 

Cost of cleaning, Lamp renewals at Annual running 
etc. ' Id. per annum. costs. 

£4 3s. 4d. 

£48 15s. Od. 

£9 15s. Od. 

£8 4s. 8d. 

£70 18s. Od. 

Table 3. — Total Cost over Five Years (including 
initial cost). 

Initial cost of Five years run- 
Installation, ning costs. 

Total cost over 
five years. 

£83 6s. 2d. £354 10s. Od. 

£437 16s. 2d. 



(figure 6) was reduced to 6 feet 9 ii 
from the walls, with the result that the 
diversity factor across the rooms 
curves for Installation 11; has been 
slightly reduced, the maximum, average 
and minimum illumination becoming 
about 5*5, 1*5 and 2"9 foot-candles 
respectively. When tin- lamps have _ 
and the decoration deteriorated to their 
fullest extent these values will fall to 
about .')•."). 2*9 and 2*0 foot-caj 

Some ides of tin- relation between 
capital and running COSts is given in the 
Tables (p. 115). 

It will be seen that in a little over a 
war the running costs including charges 
fur electrical energy equal the capital 
cost, and the important point I wish to 
emphasise is that, even with scientifically- 
gned systems giving maximum overall 
efficiency, schemes must be designed from 
theeconomical maintenance point <>f view. 

I am sure that if members compare 
the financial aspect given above with that 
of existing installations, they will find 
that the Acton Scheme presents very 
material economies taking into account 
the class of service required. 

.Mr. A. ( '. Pallot ( Engineering I division, 
H.M. < Office of Works) [communicated) : — 

By means of the coefficients of utilisation 
which have been worked out so carefully 
in the United States for different types 
of fittings and conditions of decoration, it 
is possible to predict illumination with 
some accuracy. Practically the only 
difficulty met with in Laying out semi- 
indirect installation is the uncertainty 
BS to the properties of opal ulass. Some 
samples transmit a groat deal more light 
than others, and discrimination must be 
used in selecting the bowls for any 
installation. If they are to lie used in a 
situation where ceilings rapidly deteriorate 
it is best to use the Lighter variety, 
whereas if the ceilings are likely to 
remain clean, a dense, bowl with better 
reflecting power is sometimes more 

When planning an installation it is 
necessary to make some assumption as 
to the quality of the glass, as if an average 
coefficient is assumed the number of 
points may be found somewhat excessive. 
or on the other hand the diversity mav 

be too yreat. It is very little use. how- 
ever, to sp.cify any values for trans- 
mission or absorption, as many 
manufacturers and factors have no idea 
of these properties of their products, 
and submit the most extraordinary 
figures relating to them. The only really 
satisfactory specification for a bowl 
fitting should include a polar curve under 
definite conditions of lamp wattage and 
Voltage, and position within the bowl. 
A- an approximation the candlepowex 
at two points. Bay vertically under the 
lamp and at 135 from the vertical. 
might be specified, but if this is done, 
or the polar curve is given, the placing of 
the order i^ generally nan-owed down 
to the two or three firms amongst all 
those invited to tender whose glassware 
closely fulfils the requirement.-. 
This is usually an accidental circum- 
stance, as tnosl firms tender their stock 
items, and many have no facilities for 
making measurements of candlepower. 

It will be a great step in the right 
direction when opal glassware is stan- 
dardised. Though there are practical 
difficulties in the way of making bowls 
t<- any standard of transmission and 
reflection, no doubt standardisation 
would help matters, even if it only Led 
irting bowls into grades after testing 
them. Permissible tolerances referring 
both to different parts of tin- same bowl 
and to different bowls of the same con- 
signment could also be fixed, with 
advantage both to makers and users. 

As things are at present, the carrying 
out of experiments before deciding on a 
scheme gives some advantage to the 
firm whose fittings are found most suit- 
able, since Government Departments are 
obliged to purchase by competitive 
tender. If several firms submit glass- 
ware the qualities of which approach 
those specified, the placing of the order 
becomes the usual compromise between 
quality and price. If it were possible 
to specify glassware under some such 
terms as " Grade III., Bowl Tolerance B, 
Batch Tolerance A," firms would soon 
learn that it was a waste of time to offer 
other varieties. 

Mr. C. H. Burt (communicated) : — I 
should like to add a few remarks to the 
very interesting discussion on the Paper 



read by Dr. Rayner before the Society 
on April 27th. 

The semi-indirect system of lighting 
has already found several most competent 
advocates, and I agree with them that 
under certain structural conditions, that 
system is probably the best. But there 
are other circumstances when semi- 
indirect lighting can be improved upon. 

Reference was made to the important 
questions of the relative densities of the 
semi-opaque bowls, the clarity of the 
lamp bulbs and the degrees of absorption 
depending upon the colour and the state 
of freshness of the decorations. But 
not one of the speakers referred to another 
important point — the distances between 
the source of light and the floor and 
ceiling respectively. It must be borne 
in mind that the point where it is desired 
to have illumination depends upon the 
distances through which the light rays 
have to travel. In all systems of semi- 
indirect illumination there is the loss by 
absorption in the opacity of the bowl as 
well as the loss which would be radiated 
in a downward direction if the bowl did 
not intercept and reflect those rays 
upwards, with the loss by absorption in 
the ceiling which is considerable ; lastly, 
— and this is the point I now wish to 
make — having removed the source of 
light to a height from which it would be 
the least effective, even though you were 
adopting direct lighting from the ceiling 
level, owing to the distance which the 
light rays have to travel. In my opinion, 
it is axiomatic that semi-indirect lighting 
is only an economical proposition in 
rooms wherein the lighting unit can be 
placed at approximately a mid distance 
between the surfaces to be lit, say the 
desks or work benches and the ceiling, 
and then only when height is suitably 
related to the floor area. In the case of 
abnormally lofty rooms much of the 
disadvantage of loss can be obviated by 
the provision of a false ceiling or conical 
reflector such as are illustrated in Fig. 
4, D and E. In my experience the besl 
form is E, but I advocate a reflector 1 
times the diameter of the bowl, thereby 
intercepting and reflecting the rays which 
would otherwise escape upwards. 

I venture to assert that the use of a 
ceiling as a reflector is unscientific and 
inartistic for the reasons that attention 

can best be concentrated upon a given 
object when it is well illuminated and the 
surroundings in comparative gloom. It 
is difficult to concentrate in an atmos- 
phere of light distractions, and provided 
the individual has sufficient light for his 
own operations he will do better work if 
the details of his surroundings are 
indistinct. This is a strong argument in 
favour of individual lighting and is 
certainly the most economical and adapt- 
able system with sufficient and varying 
quantity for each individual. Such a 
system, consisting either of table lights, 
standards with arms such as are used 
in banks and insurance offices, or a liberal 
provision of simple flexible pendants, if 
properly shaded, is, in my opinion, the 
ideal form of lighting if used in conjunc- 
tion with some form of diffused general 
lighting of only very moderate illumin- 
ation, forming a basis upon which to 
install efficient individual lighting. 

Such general lighting of, say, 1 foot- 
candle can, in my opinion, be provided 
by means of fixtures of a much more 
decorative and artistic nature than the 
generality of fixtures usually installed 
to provide sufficient unaided semi-in- 
direct lighting up to 3 or 4 foot-candle- 
power. Provided that entirely indirect 
methods (of which there are several, such 
as frieze lighting and the use of opaque 
bowls) are used in conjunction with some 
restful colour scheme such as an old gold 
or sea green painted surface, I know no 
objection to indirect lighting, but only 
as a basis upon which to found local 

If Mr. Cooper will allow me, I would 
like to suggest to him that his magnificent 
dome in the Port of London building 
presents an admirable opportunity of 
furnishing the space artistically and 
practically with a suitably designed direct 
lighting unit suspended at a height about 
level with the caps of his supporting 
columns, and in this manner he can 
provide agreeable lighting in every 
direction with a minimum of loss due to 
the extreme height of the apex of the 
dome. If he supplemented such a 
chandelier by bracket arms projecting 
between the columns around the walls 
he should be able to produce a delightful 
artistically-lit interior. I understand desk 
lights are already provided for. 



I wish tn add a few words on the 
subject of the flooddighting of the 
exterior of public buildings, a sample of 
which we have seen on tin- screen in the 
photograph of tin- Capitol at Washington. 

I wonder if it occurred to others as it 
did to me that the slide appeared to be 
a negative projection, and that by 
reason of the lighting being upwards from 
the ground level instead of downwards 
from the sky all the depths and surfaces 
which are. usually in shadow are shown 
in higfa light, and vice versa. I submit 
that such produces a distorted mer< tricious 
and inartistic representation and is not 
worthy of repetition in the case of our 
national monuments. Such representa- 
tions, in my opinion, are equivalent to 
the desecration if not of our buildings, 
certainly of our sensibilities. 

It is as though the Bank of England 
enlightened the dullness of its exterior 
by a moving electrical representation of 
the Benevolent <>M Lady of Threadneedle 
Street {a la Edwards' Desiccated Soup) 
serving out innumerable golden sovereigns 
from an inexhaustible money bag labelled 
1913 (a la Sandeman's Port), and I 
suggest that by a change-over switch the 
old 1 dv should be. transformed into an 
optimistic gentleman ami the direction 

of the chanism reversed whereby the 

sovereigns would be shown Sowing back 
into the same sack, now labelled Treasury. 
1 am sure the erection and working of 
such a device would In; eagerly supported 
by subscription amongst the members of 
the electrical profession in which doubt- 
less the architects would collaborate. 

Mr. R. Laxgtox Cole {communi- 
cated) : I was greatly interested in this 
Paper and I wish that many more of my 
professional bret hen had been present. I 
wish, however, that the experiments had 
not been confined to the semi-indirect 
method, when direct lighting fan be 
made quite as suitable and economical. 
I have, in mind a room in the City lighted 
with " J-watt '" lamps, the figures of 
which are as follows : — 

Area : 13,725 square feet. 

Fittings : 82, 100-watt lamps, 9 feet 
from floor, lower part of each frosted, 
each fixed below a hemispherical opal 
shade (General Electric Co.) so as to 

throw direct light on tables 2 feet 6 inches 
high, used for clerical work. 

Average area per lamp ; 167 square feet. 

Illumination : -4 candlepower. 

Total watts (nominal), 8,200. 

Watts per square feet-: - 6. 

These figures give the same results 
as Scheme II. adopted by the Office of 
Works, but the saving in cleaning of 
globes and whitening of ceiling is an 
important' advantage. The light is 
pleasant and satisfactory, and the filament 
is not visible to the eye. 

The fact brought out in the Paper 
that some .if the gasfilled '" i-watt 

lamps are not mure efficient than the old 
vacuum lamp is remarkable, and deserves 

attention. 1 SUggesI that customers 
should be able to get their lamps tested at 

convenient centres, so that they may 
not pay for what they do not obtain. 

At .mother large building. I am using 
direct lighting with large units of 500 and 
1,000 watts about 76 feet from the floor, 
and with a saving of current and improved 
light, as compared with the arc lamps 
previously installed. 

It appears to me that lighting by 
inverted bowls, though quite convenient 
and useful in many cases, is merely a 
makeshift, and that our effort should 
be directed towards the use of the brilliant 

filament of the gasfilled lamp, without 
the intervention of the bowl. I have 
observed, in a large Government Office, 
instances where the lamp has been lifted 
over the edge of bowl fittings, so as to 
increase the illumination. This practice 
seems in itself a condemnation of the 

I agree with all that Mr. Chas. 
Baker said. His remarks seem to me to 
be entirely practical. Having seen the 
Newington Sessions House, I should like 
to confirm what Mr. Baker said regarding 
the general effect. The woodwork is 
light untreated oak, and the entrance 
hall, again, is well and uniformly 

I trust that the Office of Works will go 
further with their experiments, but I 
would advise them to " try all things 
(not merely bowls) and hold fast to that 
which is good." 



Mr. A. E. Bullock, A.K.LB.A. (com- 
municated) : — Without a scientific know- 
ledge of the relative values of different 
types of globes for varying voltage 
it is not possible for me as an Architect 
to speak with experience of the results 
to be obtained under given conditions 
either from direct, indirect or concealed 
lighting, but I have made some practical 
experiments in large buildings during 
the past three years under the two latter 
systems, viz., indirect and concealed 
lighting, and the following observations 
upon these may be of interest. 

Experiments with translucent bowls, 
of the holophane, opaque and alabaster 
types with ^-watt lamps, reveal a distinct 
advantage in point of general lighting 
upon the first pendant mentioned. 

There was a fourth principle adopted, 
viz., that of reflected light by the use of 
a bowl of copper whitened on the inside, 
which being hung from a white ceiling 
reflected light throughout a large area. 
This was used in the Drawing Office 
of the Conqueror Typewriter Manu- 
facturing Company, Limited, erected 
for Viscount Lascelles — a room 29 ft. 
by 27 ft., having a clear height of about 
11 ft. with top lights over. 

It was found that there was consider- 
able advantage gained from the reflected 
light being thrown upon the ceiling 
and diffused around the room, and that 
the rays cast from a series of these 
lamps mitigated the loss of light by the 
shadow that would be expected from 
the copper bowl of the pendant. 

There are certain objections, particu- 
larly in public halls, to pendant lights — 
especially if they be naked, or can be 
seen over the top of bowls placed for 
the purpose of distributing the light 
more evenly. 

I noticed particularly the very fine 
soft, and yet light, effect obtained in 
Mr. Edwin Cooper's building at Maryle- 
bone and the photographs that were 
shown on the screen of some of the 
larger corridors and rooms, and it would 
seem perfectly possible to so arrange 
the screening of light on either side of 
beams by means of semi-opaque glass 
which would give good diffused lighting 
without the actual lights being sus- 
pended or in any way interfering with 
the view when looking through a room 

or observing an audience from a platform 
in a hall. 

In picture galleries a similar principle 
might be adopted, the lights being placed 
around the skylight at the base of the 
beam put in a false enclosure and treated 
either as point or strip lighting, and 
diffused through semi-opaque glass as 

It seems very obvious to me that the 
lighting of the future will be either the 
concealed type reflected from light 
surfaces or be cast by means of search- 
lights upon the flood-light system adopted 
in New York. Where, of course, specially 
fine work has to be done, plugs can 
easily be provided for special lamps. 

There is another system which was 
not mentioned at this discussion, viz., 
that adopted by the Sheringham Daylight 
Development Company, which is a 
combination of both the indirect and 
the concealed lighting. The distinctive 
merits of this particular system is that 
the light can be automatically changed 
in colour. 

In most buildings erected by architects 
there is usually a fairly big cornice pro- 
jecting sufficiently to allow of the lighting 
being placed along its top surfaces. This 
system was successfully adopted by me 
last year in the lighting of a cinema at 
Loughborough, it being so arranged that 
the full volume of light could be obtained, 
or it could be dimmed according to the 
requirements of the operator, so that 
when dimmed it was possible to clearly 
see a picture upon the screen although 
the lights were on, and one could also 
see to get about the building for the 
purpose of egress. 

The whole question of the illumination 
of large centres such as halls, board 
room, etc., should be considered at the 
time of their being planned by the 
architect, as it must not only affect the 
estimate of the work, but would be 
beneficial, if well thought out, in the 
general treatment of the apartment. 

It is obvious, too, that the denser the 
colour upon the ceilings or walls, the 
greater the loss of light from however 
powerful a lamp there may be fixed 
thereto. In the case of the cinema 
above mentioned, the cove, which was 
a very deep one, was painted a pale 
apple green, but in point of fact when 



the colour was fixed it was found to be 
three shades darker than was intended, 
and consequently the plaster at the 
extreme bottom of the cove, where it 
abutti-d on to the top of the cornice, was 
left white to allow as much reflection as 
possible. In certain eases it is a simple 
matter to place mirrors to assist in the 

Mr. J. \Y. Jones (communicated) : — I 

have listened with very great interest to 

the most useful Paper which the. authors 

have presented to-night, and think that 
although a considerable amount of in- 
formation concerning the effectiveness 

and residts which may lie obtained from 
different kinds of fittin-is is available 
both in the literature of this country 
and that of America, yet it is the 
time that such full and comparative data 
has been available. 1 congratulate the 
authors upon the very painstaking work 
which they have accomplished. 

When dealing with the lighting of 
importanl squares and cros>ine.>. in order 
to judge the effectiveness and uniformity 
of the illumination, 1 have made a habit 
of preparing contours of various inten- 
sities of illumination. It is possible from 
the consideration of such contours to 
rapidly pick out faults of installations 
and at a glance determine the degr< 
uniformity over the ar 

I am rather inclined to think, there! 
that the data provided by the authors 
would have been of still greater value if 
contours bad been prepared showing the 
illumination of the areas with different 
methods of lighting. 

I have roughly prepared contours from 
the available information of installations 
I. and II.. and it is quite obvious from a 
very casual inspection that the illumina- 
tion in the second case is more uniform 
than that in the first. The entire area 
has an illumination of between -"i and 5 
foot-candles, whereas in installation No. 1 
the blotchy character of the contours 
shows how' uneven the lighting is. 

The authors have spent a considerable 
amount of time and trouble in obtaining 
the utilisation and factors of different 
methods of lighting, and I would sin. 
that a more accurate method of obtaining 
these efficiencies would have been to plot 
the contour and measure the areas of 

different intensities by means of a plani- 
meter and effect the summation. It 
would seem that such a course would 
give considerably different results from 
that of taking average figures as the 
authors appear to have done.. I am 
quite aware that the work involved in 
doing this would be somewhat laborious, 
but in view of the fact that basic riirures 
are aimed at, it would have been well 
worth the time and trouble. 

I am rather inclined to disagree with 
the rem arks that Mr. Haydn T. Harrison 
made concerning the literature which is 
available on the subject of this Paper. 
It is quite true that there is a large amount 
of information of installations of all kinds, 
but this is the first time that really 
comparative data of this order has been 
available. It should prove of consider- 
able value to illuminating engineers and 

The ArriioHs (in reply, communicated) 
wished, first of all. to express their 
thanks for the appreciative way in which 
their paper had been received. It was 
extremely gratifying to know that the 
results obtained had awakened such a 
wide interest and had proved the means 
of provoking Bucb an interesting dis- 

In reply to several speakers who had 
expressed regret that only the semi- 
indirect system had been tried, they 
would like to say that the urgency of the 
problem had been such that it was 
necessary to restrict the experimental 
work as far as possible. The Committee, 
which had been set up to advise on the 
work, and on which several Government 
Departments were represented, had come 
to the conclusion, on the results available 
to them, that semi-indirect lighting was 
the most promising system for this 
particular design of building, and for the 
work carried out in it, The experiments 
were, therefore, restricted to this system. 
It by no means followed that direct or 
totally indirect lighting systems might 
not be employed in other installations 
where different conditions prevailed, and 
in that case it was to be hoped that 
experiments of a similar nature to those 
described would be undertaken. 

The influence of deterioration, men- 
tioned by Major Gunton and other 



speakers, was, of course, very important. 
There had been no opportunity of making 
measurements of this effect in the Acton 
building, but the Committee already 
referred to had kept this factor in mind 
when proposing an average illumination 
of at least three foot-candles as the 
standard to be attained when the in- 
stallation was new. 

Several speakers had mentioned the 
need for further information on daylight 
illumination. The authors agreed that 

brought to the notice of the National 
Physical Laboratory from several sources. 
It was very important that recognised 
qualities should be available, and some 
preliminary steps had been taken with 
a view to making definite progress 
towards this end, for without some 
assurance as to the limits of quality of 
the fittings which would be installed, it- 
was impossible to design a system of 
illumination with any certainty that it 
would conform to the conditions required. 

Contour Curves for Installation No. I. 

Contour Curves for Installation No. II. 

this was an extremely important matter, 
and it was probable that some of the 
earliest experiments carried out in the 
experimental illumination building at 
Teddington would be directed to the 
determination of some of the doubtful 
factors in the planning of the natural 
lighting of a budding. 

The importance of the measurement 
and, if possible, the standardisation, of 
the absorption and reflection factors of 
translucent glass, which had been men- 
tioned by many speakers in the course 
of the discussion, had already been 

The authors were unable entirely to 
agree with Mr. Burt's remarks concerning 
flood-lighting. If the monument were of 
a kind suitable for such treatment, and 
convenient positions were available for 
the projectors, there was no reason 
whatever why flood-lighting should not 
be advantageously used far more ex- 
tensively than at present. 

As regards Capt. Stroud's remarks on 
the diversity factor, it should be men- 
tioned that the lowest value of the 
illumination measured in this installation 
occurred at the end of one of the side 

1 52 


rows, in a bay where there was only one 
lamp, and near a wall whose reflection 
ratio was considerably lower than that 
of fche others. The final scheme adopted 

in a room twice the size of the experi- 
mental room would provide additional 
illumination at this point, with a con- 
sequent reduction in the diversity factor. 


An Important Light and Air Judgment. 

A case of considerable interest was 
recently settled before Mr. Justice Eve 
in fche Chancery Division. The plaintiffs, 
Messrs. Semon & Co., Ltd., of Bradford, 
claimed against the Bradford Corporation 
an injunction restraining them from 
erecting an electric light station on fche 
north side of Balme Street, Bradford, in 
such a manner as to cause an obstruction 
to fche light of fche windows of plaintiffs' 

Mr. P. J. Waldram gave expert evi- 
dence on behalf of the defendants, pre- 
senting the results of photometric tests 
in support of his news, and the case is of 
considerable interest as illustrating the 
legal importance now attached to scientific 
measurements of daylight. 

Largely as a result of this scientific 
evidence the case was won by fche de- 
fendants. In view of the importance of 
the proceedings, we reproduce the account 
of Mr. Justice Eve's summing up, which 
has appeared in The Architect's Journal:— 

Mr. Justice Eve, in fche course of his 
judgment, said: The width of Balme 
Stn-.t between the two frontages is 45 ft., 
an I the defendants' building will be co- 
terminous with the plaintiffs' premises for 
a distance of 21 ft. 8 in. along Balme 
Street. As a result it is directly opposite 
the two most easterly windows on the 
ground and upper floors of the plaintiffs' 

warehouse. From these windows it will 

cut off on the ground floor 48 per cent, 
and 41 per cent., and on the first floor 
41 per cent, and 33 per cent., of the 
direct li^ht heretofore reaching them. I 
do not propose to deal with any windows 
other than these four. I think Sir 
Bannister Fletcher — fche plaintiffs 1 lead- 
ing expert — made a perfectly proper ad- 
mission when, in answer to this question, 
referring to the four westerly windows on 
each floor : " What I am asking you to 
-a\ is thai with regard to these windows 
no reasonable man, and certainly no dis- 
tinguished professional man, would go 
into the hox and say they were seriously 
interfered with in such a way as to give 
in his opinion any right of complaint," he 
replied: "1 think it is quite likely." 
And again, when at the very end of his 
cross-examination, he was asked : " You 
do not really seriously suggest, do you, 
thai on the second floor on that staircase 
there is going to be any ground of com- 
plaint with regard to light when the 
building is up ? " and deliberately ab- 
stained from giving an affirmative answer, 
contenting himself with the observation : 
" I think it may well he a light staircase," 
he surely must be treated as assenting to 
the suggestion underlying the cross - 
examiner's interrogatory. 

What . then, is the issue I have to try ? 
It is this: Will the erection of the de- 
fendants' building obstruct the access of 
light to all or any of the four easternmost 
windows — two on the ground floor and 
two on the first floor — of the plaintiffs' 
premises to such an extent as to render 
those premises substantially less con- 


I 53 

venient for beneficial use and occupation 
as a warehouse for the purposes of the 
plaintiffs' business ? 

I think it may be questioned whether 
the plaintiffs when they closed their case 
had discharged the onus which rested on 
them of proving that the defendants were 
threatening and intending to take away 
so much of their light as to leave them 
less than is required for the beneficial vise 
of their warehouse for the purposes of 
their business. But even if the plaintiffs 
raised a prima facie case of an actionable 
interference I think it was rebutted by 
the evidence given on behalf of the de- 
fendants. In particular I rely upon 
Mr. P. J. Waldram, whose testimony was 
given with commendable impartiality 
and with great lucidity. 

The evidence given on behalf of the 
defendants proves a room to be ade- 
quately lighted for the purposes of adult 
clerical work so long as the illumination 
at the worst lighted working point in the 
room does not fall below 0'4 per cent, of 
the sill light. I ought to add that the 
light is measured in all cases at table 
level — that is 3 ft. above the floor. 

On this basis Mr. Waldram measured 
the light in the areas of the plaintiffs' 
premises lighted by the four windows 
with which I am dealing. He selected on 
the ground floor as the worst lighted 
point in the triangular area lighted by the 
two easternmost windows, a point in the 
rear some 15 ft. behind the front wall, and 
about half way along the imaginary line 
forming the third side of the triangle. 
In existing conditions with the thick 
hammered glass in the windows, and with 
the iron grilles in front, but with no 
building opposite, he measured the day- 
light factor at that point as 1"4 per cent, 
of the sill light. He then proceeded to 
calculate by means of diagrams which are 
in evidence what the measurement at the 
same point will be if the defend 
building is erected and ordinary plain 
glass substituted for the hammered plate 
glass, and he finds the daylight factor in 
these circumstances will be 1*5 or 1*6 per 

cent., and says that this result shows that 
the lighting conditions on the ground 
floor will be "distinctly good — very dis- 
tinctly above the average — quite ade- 
quate for the ordinary requirements of 
ordinary people carrying on a business of 
this kind in this sort of situation," adding 
" I think I may go further and say that in 
my opinion they will remain unusually 
adequate," and a little later, " Taking the 
area affected by the defendants' building 
the ground floor should remain with 
normal conditions" — that is, of glazing 
and cleanliness — "a well-lighted and an 
unusually well-lighted ground floor." 

On the first floor, after stating his 
opinion that the office lighted by the 
three easternmost windows will remain a 
thoroughly well-lit office after the de- 
fendants' building is up, he proceeded to 
give the results of his tests and calcula- 
tions. The worst lighted point in the 
room he puts in the angle above the 
telephone box — the worst lighted working 
point at the south end of the long desk 
against the east wall of the room. At the 
former the illumination will be - 8 per 
cen t. — twice the measurement at the 
grumble point, and at the latter 154 per 
cent, of the sill light— one and a half 
times the minimum of an elementary 

In the face of this evidence, strength- 
ened by a careful comparison of the 
relative proportions of floor and glazed 
window areas, unshaken by cross-exam- 
ination and unchallenged by any 
satisfactory practical tests on behalf of 
the plaintiffs, it is impossible for me to 
hold that the plaintiffs have discharged 
the burden of establishing that the 
defendants' operations will constitute an 
actionable nuisance. The evidence 
proves, I think, that the plaint i Its- 
warehouse is and will remain in enjoyment 
of an unusually large amount of Light 
having regard to its locality, and in these 
circumstances I can only dismiss the 
action with costs. 




[At the request of many of our readers we have extended the space devoted to 
tliis Section, and are open to receive for publication particulars of interesting 
installations, new developments in lamps, fixtures, and all kinds of apparatus connected 
with illumination. 

The contents of these pages, in which is included information supplied by the 
makers, will, it is hoped, serve as a guide to recent commercial developments, and we 
welcome the receipt of all botia-fide information relating thereto.] 

BROTHERS & Co., Ltd., Thursday, 
May 18th, 1922. 

A Press Visit to the above works was 
:n ranged on Thursday, May 18th, visitors 
assembling outside the premises ol Messrs. 
English Electric & Siemens Supplies, 

seven years. The work is carried on in 
a well-equipped six-storey building, and 
has evidenl ly extended considerably. The 
sequence of operations now takes place 
in a very orderly and convenient manner. 
Whereas up to 1913 the factory was ex- 
clusively engaged in making straight 
filament vacuum lamps, it is now devoted 
t<> the manufacture of gasfilled spiralised 

View of the Dalston Works from approach to Main Entrance. 

Ltd., at 38-39, Upper Thames Street, 
whence they were driven to the Dalston 
Factory and received by Mr. Le Marechal. 
Readers may recall that in 1914 we 
described a visit to these works.* It was 
interesting to observe the developments 
that have taken place in the subsequent 

* Illum. Eng., Nov., 1914. 

types. One feature that struck us was 
the improvement in the lighting arrange- 
ments. It is common knowledge that in 
lamp factories the lighting is sometimes 
carried out in a very casual manner. It 
was satisfactory to observe that up-to-date 
lighting fittings are now installed through- 
out, one good feature being the complete 
shading of the rows of local lamps used on 



benches, so that the light is directed 
downwards on the work, and the filament 
screened from the eyes of operators. 
Another item that calls for comment is 
the installation of a considerable amount 
of automatic machinery, much of which, 
we were informed, had been designed by 
the company's technical experts. Amongst 
such machines may be mentioned those 
for spiralising tungsten wire — a delicate 
process, requiring modification according 
to the size of wire treated — and for 
making pigtail loops for filaments. The 
latter machine is particularly neat in 

The general process of making incan- 
descent lamps has been described before 

diminishing diameter. These dies natur- 
ally tend to become irregular La section 
in course of time. They are accordingly 

examined under the microscope at regular 
intervals and polished to uniformity 
when necessary. The nature of the 
tungsten metal, prior to the drawing of 
wire, and also as present in the complete 
filament, is also examined closely by 
photo-micrography and visitors were 
shown the process of making such micro- 
photographs. Records are available 
showing the variation in macro-structure 
of the metal in different circumstances. 

The wire having been produced the 
process of spiralising begins, the wire being 
wound on a mandrel, but automatically 

Swaging and Wiredrawing Machines. 

in our journal, and is familiar to reader-. 
Operations fall into three main divisions — 
the making of the filament, the treat- 
ment of glass bulbs involved in setting 
the filament in position, and the ex- 
haustion and filling of the lainp-bulbs 
with suitable gas (in the case of gasrilled 
lamps). The commercial oxide of tung- 
sten is purified in the laboratory and 
reduced to grey tungsten metal powder 
by heating in a current of hydrogen. The 
powder is pressed into sticks 7 in. long 
and J in. square, baked, and then sintered 
at white heat by the passage of an electric 
current in an atmosphere of hydrogen. 
This sintered "slug" is then p 
through a hammering machine and re- 
duced to J in. in diameter, and is then 
gradually drawn into the required thick- 
ness of wire by passing successively 
through diamond dies of progressively 

divided into suitable length- for filaments 
by intervals of straight w ire. 

Meantime the glass bulbs are washed 
in acidulated water and cleaned for use. 
and the processes leading to the fixing 
of the filament are undertaken. These 
processes including (a) cutting the glass 
tube to form the foot of the lamp: (b) 
flanging of the tube, done by automatic 
machines fed from a magazine filled with 
sections of tube : (c) preparing the lead- 
ing in wires ; (d) making the solid glass 
stem which ultimately carries the radial 
supports for the filament ; (e) assembling 
the foot, the leading in wires and sten 
being fixed in position in the flanged tube 
and the lower end of the tube hermel ically 
sealed by a " pinch " in a gas flame ; 
(f) the building up of the spider on the 
glass stem, the design varying somewhat 
for different types of lamps. 



The process of filamenl mounting com- 
prises (a) the mounting of the pigtail 
hooks ; (b) the spot-welding of leading in 

wires t<> metal tajx- electrodes, where 
necessary ; (c) the testing of spirals 

pose of sealing in the foot and filament 
within the bulb. A feature of interest 
is the construction of "pipless" lamps, 
and it may be mentioned that in the 

i tam forms of gasfilled lamps the 



1 '.'fl«B|r; : 


Section "f the Exhausting and Casfilling Department. 

Section of Photometric Department, sho\vin_ r Sphere Photometer in 
corner of room. 

before mounting ; and (d) flashing the 
filament to remove, by chemical means', 

any traces of the lubricant used in 
drawing the wire. 

Special machines are used for the pur* 

pip is located inside the cap of the lamp so 
thai a perfectly uniform bulb is obtained. 
The lamps are next exhausted by 
special rotary oil pumps. (lasfilled 
lamps are then fed with inert gases 



INDEX, May, 1922. 

Editorial. By L. Gaster 

cHlumtnatfng jBngineertnq Society— 

(Founded in London, 1909) 

The Lighting of Public Buildings (Discussion)— Capt. W. J. Liberty- 
Mi-. F. A. Llewellyn— Mr. P. J. Waldram— Major H. C. 
Gunton — Mr. Chas. A. Baker — Mr. G. Campbell — Mr. Haydn 
T. Harrison — Capt. E. Stroud — Mr. A. Cunnington — Mr. A. G. 
Ramsey— Mr. A. C. Pallot— Mr. C. H. Burt— Mr. R. Langton 
Cole — Mr. A. E. Bullock — Mr. J. W. Jones — Dr. E. H. Rayner, 
Mr. J. W. T. Walsh, and Mr. H. Buckley (in reply) 

Daylight, Access of. An Important Light and Air Judgment 

Topical and Industrial Section : — 

Press Visit to the Dalston Works of Messrs. Siemens Brothers and Co., 
Ltd. — Light in the Home — Figures and Facts for the Salesman — 
Street-Lighting by Gasfilled Lamps, etc. 





(usually nitrogen or argon) at a suitable 
pressure, a feature being the very careful 
purification of the gas used, and the pro- 
vision of four interchangeable som'ces of 
gas supply. 

In the photometry room several 
benches equipped with grease-spot photo- 
meters were in use. Of special interest is 
an Ulbricht sphere equipped with Lummer 
Brodhun photometer for testing mean 
spherical candlepower, which is proving 
of considerable value for the testing of 
gasfilled lamps. Finally there an- the 
processes of capping and stamping lamps. 
with particulars of voltage, watts, etc., 
and a final test before lamps leave the 
factory. At every stage of the foregoing 
series of operations checking tests are 
applied, so that the proportion of lamps 
that fail to pass the final test is very 

Apart from the standard types of 
lamps, there are many special variel ies t<> 
be seen at the Dalston factory. Amongsj 
these may be ' mentioned the "Siemens 
Traction " Lamp, the filament of which 
is specially arranged to promote concen- 
tration of light and great strength, varied 
types of automobile lamps, and the 
" Silvalux " lamps, the feature of which 
is the use of a bulb made entirely of opal 
glass, and therefore giving a very soft 

light. Special interest also attaches to 
the new daylight gasfilled lamp, having 
a bulb of blue glass designed to convert 
the light into a close resemblance to day- 
light. This is stated to be proving very 
useful for work where correct appearance 
of colours is important. 

A very interesting historical exhibit of 
lamps of all kinds is also to be seen in the 
small museum which has been arranged 
in the factory. 

Following the visit to the factory the 
party was entertained to lunch at the 
Hoi born Restaurant, terminating a most 
enjoyable morning. 


We are informed that Messrs. English 
Electric & Siemens Supplies, Ltd., have 
received from the London County Council 
an intimation accepting their tender for 
the supply of electric lamps for the 
ensuing twelve months. 

This contract covers the supply of 
" Siemens Traction" type lamps for tram- 
car lighting throughout their system, 
standard vacuum and gasfilled lamps to 
meet t heir various requirements, and a No 
automobile lamps. 

1 58 



An attractive series of photographs, 

illustrating modern domestic gas lighting, 
is included in a recent issue of "A 
Thousand and One Uses for Gas." There 
are views of panelled halls, dining and 
drawing moms, etc., lighted by pendant 
units screened by silk shades, and 
several examples of effective bracket 
lights over ornamental mantelpieces and 
fireplaces; in the smoking room a gas 
cigar and cigarette lighter is also provided, 

Other pictures refer to the lighting of 
bedrooms, kitchen and bathroom, where 
the use of vitreosil glassware is strongly 
recommended. Special importance is 
attached to the elimination of glare. 
Apart from the obvious importance of 
domestic lighting to the comfort of the 
home, its bearing on the eyesight of 

children should not he overlooked, and 

we are glad to note that attention is 
being devoted to this subject. 


Under the above title, a series of 
articles contributed to the Gas Journal 
by ISlr. W. A. Bishop (Croydon Gas Co.) 
has been reproduced in pamphlet form. 
Comparative data for the cost of gas and 
electricity for lighting, cooking, heating 
and other uses are given and ventilation 
and hygienic aspects are discussed. We 
notice that in dealing with lighting, 
comparisons are made in terms of candle- 
power per consumption of gas or elec- 
tricity, which no doubt is the basis that 
has the most general application. The 
aut bor recognises, however, t hat wherever 
possible running expenses should be 
compared on the basis of giving a certain 
mean illumination in foot -candles. 

We quote with pleasure Mr. Bishop's 
introductory remarks leading up to the 
presentation of this data : — " The fact is 
worth bearing in mind that it never pays 
to underrate a competitor ! ... It 
seems a great pity to the writer that at 
times — on both sides — one sees (and 
encounters) disparaging and discourteous 
remarks that would have been better 
left unsaid or not written. Commercial 
rivalry is good for everybody (it keeps 
us alive !) but let us have fair com- 
petition. Gas and electrical salesmen 
will do well to remember that their 
methods, whether they be 'above' or 
' below board ' — are most certainly bound 
to ' boomerang* for good or bad." 


A booklet, issued under the above title 
by the General Electric Co., Ltd. (Magnet 
House, Kingsway, W.C.2), contains some 
general recommendations on street light- 
ing, and a photograph of Oxford Street, 
which is described as •"The Best Lighted 
Street in London." The average illu- 
mination is given as 2"1 foot -candles. 
Definitions of the chief photometric 
quantities and elementary methods of 
calculation are given, and there is a 
description of the " Directive " system of 
street lighting. The Longitudinal Light- 
ing Lanterns (Harrison's Patents) are 
illustrated. It will be recalled that a 
feature of this lantern is the use of two 
inclined mirrors immediately adjacent to 
the lamp, whereby the natural curve of 
light distribution is materially altered 
and rays are directed to the parts of the 
street most remote from the lamp. Polar 
curves and diagrams illustrating results 
obtained with such lanterns are pre- 
sented. In a typical case of lanterns 
25 feet above street level, spaced 150 
feet apart, a maximum of approximately 
one foot-candle and a minimum of 0*2 
foot -candle are recorded. 

Another form of lantern illustrated 
(the "' Metropolitan ") employs the well- 
known Holophane Refractor glassware, 
and is recommended as particularly 
suited for use in main streets where tall 
standards are employed. 


Some attractive literature has 
issued by the General Electric Co., 
(Magnet House, Kingsway, W.C.2), 
trating the new "" Osglim " neon 
which arc stated to consume onl\ ."> 
on 200-260 volts, and to give 25 
light for one penny. Apart from 
use for luminous letter-signs, these 
have special applications for night- 
pilot lights, etc. 

, Ltd. 
, illus- 


We have received from the Swedish 
General Electric Co. two stock lists, 
No. Ill and 111a, illustrated D.C. and 
A.C. machines. These appear to cover a 
wide range of machines, and particulars 
of starters are also included. In addition 
to standard D.C. motors, special motor 
generator sets for cinema work are in- 
cluded, and single phase and two and 
three phase induction motors are listed 
in a variety of types. 



Sdifed. /C^> 




^Humiliating Engineering Society. 

(Pounded in London, 1909.) 


Tel. No. Victoria 5215. 


The Use of Light in Hospitals. 

The use of light in hospitals comprises many questions on which 
much remains to be learned. Setting aside, for the moment, the thera- 
peutic applications of light, i.e., its direct use as a curative agent, there is 
ample room for investigation in connection with problems of illumination. 
Here we find a great diversity of practice, arising doubtless from the fact 
that responsibility for lighting is not always allocated in the same way. 
Decisions may be influenced by the views of the permanent medical staff, 
the consulting surgeon, or the electrical engineer attached to the hospital. 
More care is devoted to lighting in some hospitals than in others. But 
there are at present no generally accepted rules, such as would serve as a 
guide throughout the medical profession. Following their usual practice 
of promoting co-operation between the expert and the actual user of light, 
the Illuminating Engineering Society accordingly arranged for a joint 
discussion with the Royal Society of Medicine (Sections of Surgery and 
Ophthalmology) on April 27th. 

The introductory paper by Mr. John Darch was supplemented by a 
series of queries, which are reproduced in this issue (p. 164), with the object 
of inviting information. Some of the chief problems in the use of light 
in hospitals are mentioned in this list. In the discussion before the Society 
attention was devoted mainly to two of the most important of these, 
namely, the lighting of wards and operating tables. 

It would appear that experts are in general agreement on the main 
principles to be adopted in the lighting of wards, though they are not 
always followed in practice. One of the most important of these is doubtless 
the avoidance of glare in the eyes of a patient, either from lamps above the 
bed or from similar lamps on the other side of the ward. Requirements 

n;u ti i i: [LLUMINATING ENGINEER (jttne 10-- 

will probably be met readily by semi-indirect lighting, but if this method 
is used, scrupulous care in keeping the bowls free from dust is necessary. 
Various methods of shading are suggested in the paper, and possibly the 
use of small lamps with opal ^la>s bowls would afford a simpler solution of 
tin- problem. Flexibility in lighting, enabling the illumination to be 
diminished to a suitable low value at night, is also desirable. 

The question that proyoked most discussion was the lighting of 
operating tables. The requirements here are somewhat exacting. A 
high illumination on the tables, preferably not less than 25 foot-candles, i- 
considered n< ci ssary. The apparatus must be so designed and placed 
that there is no likelihood of trouble owing to dust falling on the table, 
nor of the fitting casting inconvenient shadows when daylight is in use. 
Special attention should lie paid to the direction from which the light 
comes, with a view to avoiding troublesome shadows being east by the 
head or arms of the operating surgeon. While surgeons agree that a 
good diffusion of light i- desirable, they apparently do not desire an 
illumination that might be termed " shadowles Doubtless the exact 

degree of diffusion would depend on the nature of the operation, and 
there is evidently room for further investigation. Most surgeons prefer 
to carry out critical operations by daylight. Vet it is conceivable that 
artificial light, which is free from the extreme variation of daylight, 
and under better control, would answer the purpose even better, provided 
the required conditions can 1m- fully determined and realised in practice. 

Colour of light, besides high intensity, is doubtless of importance in 
many sections of medical work, and it would seem that systems of artificial 
daylight might prove valuable, ft is necessary, however, to obtain a 
considerably higher order of illumination than is usually available at 
present from artificial daylight units. 

Attention was also drawn to some problems in the design of portable 
examination lamps, especially for ophthalmic work, of which some examples 
were shown by Mr. |. B. Reiner. The chief difficulty is to secure a 
sufficiently strong and even illumination, five from striations due to images 
of the filament being formed by the system of projecting lenses. Experi- 
ments with such lamps have recently been made, and while the desired 
conditions can be met with comparative case by using a low yoltage lamp, 
they are less easy to comply with in the case of lamps capable of being 
used on an ordinary supply voltage. However, considerable progress in 
this respect has been made, and with the aid of leading lamp manufacturers 
suitable forms of lamps should be ultimately obtained. It is evident 
that many of the lighting problems met with in hospitals can only be 
effectually solved with the assistance of the research departments of lamp 
manufacturers, and we have here an instance of a field in which they can 
do particularly useful public service. The Illuminating Engineering 
Society, which includes amongst its members both lamp manufacturers 
and members of the medical profession, is in a specially favourable position 
to deal with such problems. 

It would be of great use to the medical profession if some general 
recommendations in hospital lighting, which would act as guide to those 
in charge of the hospitals throughout this country, could be prepared. 
It was suggested at the discussion that a small joint committee representing 
the Illuminating Engineering Society and various sections of the medical 
profession would be helpful, and the Society will deal with this matter 
very shortly. 


Lighting Requirements in Medicine and Dentistry. 

It is interesting to observe, as showing the similarity in progress in 
illuminating engineering in both countries, that the Illuminating Engineer- 
ing Society in the United States has likewise been considering the Use of 
Light in Medical Professions. The transactions of the Society for January, 
1922, contains a series of papers on the subject. Thus, a paper by Louisa 
P. Tingley, M.D., summarises the replies received to a series of queries 
addressed to ophthalmologists, otolaryngologists and dentists. The 
replies indicate that very different lighting arrangements are in use by 
such experts. It is remarked, however, that physicians and surgeons prefer 
strong daylight for the general examination of patients. The author, 
nevertheless, considers artificial light preferable for the illumination of 
optical test-charts, as the maintenance of a standard illumination is im- 
portant in its bearing on visual acuity. We are glad to see that Dr. Tingley, 
when taking a patient's history, makes inquiries into the conditions of 
natural and artificial lighting under which they usually work. If oculists 
would make a practice of inquiring into these conditions when seeing 
patients, information of great value to the illuminating engineer should 
ultimately be accumulated. 

Mr. T. Maijgren gives a brief account of surgical lamps for the examina- 
tion of passages in the body. The " nasopharyngoscope," when intro- 
duced through the nostril, for example, enables the physician to see clearly 
internal organs and cavities which could never be seen properly before, 
except during a post-mortem examination. Such instruments, which 
necessarily utilise a very small glow lamp, often associated with lenses 
and prisms so as to form a species of periscope, demand very careful design. 
One point that needs attention from designers is that such apparatus needs 
to be thoroughly sterilised before being used again, and its parts must, 
therefore, come apart easily and be capable of being " boiled " without 

This condition applies equally to the special lamps used by dentists 
and discussed by Dr. Percy Russell. A dentist always aims at obtaining 
good access of daylight into his workroom. There are, however, many 
rooms in which natural lighting is poor, and it is often desirable to be 
able to work by artificial light. Of late, dentists have been quick to 
perceive the value of suitable artificial daylight, as correct judgment of 
colours is often of great consequence in their work. It is remarked that 
an arrangement enabling artificial daylight gradually to take the place of 
natural light, without the change being apparent, when daylight fails, would 
be extremely valuable. But in view of the fact that he has to examine 
closely cavities in teeth, a local source of light within the mouth is essential. 
The need can be met in a measure by the usual reflecting minors (some of 
which have been equipped with blue glass to convert artificial light into 
artificial daylight). But there are cases when an actual lamp within the 
mouth is needed. One question of interest raised in this and preceding 
papers is that in the examination of teeth, throat or eyes the patient has 
often to face a strong light and the possibility that this will prove trying 
to vision should be guarded against as far as possible. 

B 2 


The Action of Light upon the Human Body. 

Considerable interest attaches to the work of the Committee, recently 
appointed by the Medical Research Council, to advise them upon " the 
promotion of researches into the biological actions of light, with a view 
to obtaining better knowledge of the effect of sunlight and other forms of 
light upon the body in health and disease." The Chairman of the Com- 
mittee, Professor Sir William Bayliss, whom we take this opportunity of 
congratulating on his well-merited Knighthood, is a member of Council of 
the Illuminating Engineering Society, who has on several occasions con- 
tributed to discussion on the effect of light upon the human eye. 

The investigation is concerned both with sunlight and other forms of 
light, so that it covers a wide ground. In view of the fact that we become 
aware of light primarily through the action of the human eye, the effect of 
different forms of light on this organ are naturally of special importance. 
In dealing with lighting problems we are constantly being made aware how 
greatly the help of the ophthalmologist and physiologist is needed. There 
are many questions, such as the origin of glare and the effect on the eye 
of excessive contrasts in brightness, that are essentially physiological in 
scope. How greatly, for instance, our efforts to make recommendations 
for the avoidance of glare would be simplified if there existed a readily 
applied test, by which one could recognise whether conditions were glaring 
or not ! 

Similarly, when we come to study the effects of inadequate lighting 
in causing industrial fatigue, or the effects of peculiar conditions on the 
eyes of workers in certain industries, we at once find ourselves limited by 
lack of data on the physiological side. Of the effects of ultra-violet light 
something is known, but there docs not appear to be much authoritative 
information on the effects of visible light of different colours, and the 
influence, if any, of such variations in colour as exist in the light from the 
chief illuminants. 

The question of the effect of variations in the intensity of daylight 
alone offers a fruitful ground for study. There is a general impression that 
inadequate access of daylight into a building is prejudicial to health, and 
that those whose occupations demand their working mainly under artificial 
light may suffer. But it would appear that we have at present little 
knowledge of the precise physical effect of the great variations in intensity 
of daylight that occur in summer and winter, and the still greater seasonal 
variations experienced by those who live in extreme northern latitudes. 

The inquiry, therefore, leads us to hope that many matters on which 
we are looking to the medical profession for guidance will be studied. We 
recognise that these are complex problems, for the study of which much 
time is needed. But the formation of this Committee provides a means of 
initiating the necessary researches, and we arc confident that the various 
problems we have mentioned will receive sympathetic consideration. If 
opportunity arises, the Illuminating Engineering Society would doubtless 
gladly co-operate with the Committee, both by offering suggestions for 
desirable researches and by participating in those that fall within its sphere 
of action. 

Leon Gaster. 





Gbc 3lluminatino JEngincertno Society. 

(Founded in London, 1909.) 

The Illuminating Engineering Society is not, as a body, responsible 
for the opinions expressed by individual authors or speakers. 


(Proceedings at a Joint discussion arranged by the Illuminating Engineering Society in con- 
junction with the Royal Society of Medicine [Sections of Surgery and Ophthalmology], held 
at the House of the Royal Society of Arts, 18, John Street, Adelphi, W.C., at 8 p.m., 
on Thursday, April 27th, 1922.) 

A meeting of the Society was held at 
the House of the Royal Society of Arts 
(18, John Street, Adelphi, W.C.) at 
8 p.m., on Thursday, April 27th, The 
President (Sir John Herbert Parsons, 
C.B.E., F.R.S.) presiding. The minutes 
of the last meeting having been taken as 
read the Hon. Secretary read out the 
following names of applicants for mem- 
bership : — ■ 

Member : — 

Thos. Terrell, Jr. 

Associates : — - 

C. J. McGowan 

C. V. Rae 

The names of applicants announced at 
the last meeting on March 28th wen; read 
out again, and these gentlemen were 
formally declared members. 

The Chairman then called upon Mr. 
J. Darcii to read his introductory paper, 
opening the discussion on " The Use of 
Light in Hospitals.'* An interesting dis- 
cussion ensued, in which the following 

took part : Prof. C. C. Choyce (Univer- 
sity College Hospital). Mr. W. R. Holmes 
Spicer, Mr. J. W. Jones, Mr. Conrad 
Beck, Mr. A. Wilson, Mr. J. B. Reiner, 
Mr. F. S. C. Raphael, and Mr. E. W. 
Johnston (King's College Hospital). 
Mr. J. Darch having briefly replied to 
the discussion, votes of thanks were 
accorded to the Author and the Chair- 
man. In conclusion, The Chairman 

Consulting Chemist, 32, Queen's Avenue. 
Muswell'Hill, London, N. 10. 

6, Church Hill. Sligo. Ireland. 

Electrician, 10, Gaupur Extension, 
Basananagudir.0..1 ) >angaloiv.S. India. 

announced that the Annual Meeting 
would he held on Thursday, May 25th, 
when the Presidential Address would be 
delivered. He also mentioned that an 
invitation had been extended to members 
of the Society to attend a meeting of the 
Optical Society, to be held at 7.30 p.m. 
on May lltli, when there would be a 
discussion on " Motor Headlights." 




(The following queries were prepared as an introduction to the Joint Discussion on the 
above subject, which to >k place at the Joint Meeting of the Illuminating Engineering Society and 
the Royal Society of Medicine on April 27th, 1922.) 

(1) Lighting of Hospitals in General. 
What special arrangements are con- 
sidered necessary for the general lighting 
of hospitals, e.g., as regards (a) choice of 
lamps and fittings to avoid harbouring of 
• lust and facilitate easy cleaning : (b) 
provision of alternative lighting supplies 
or systems in the interests of safety ; (c) 
the arrangement <>f the switches in certain 
cases (asylums, etc.) in such a manner 
as to be only accessible to the staff and 
not Bubjecf to interference, and (i>) choice 
of colours for walls and ceilings bo as to 
ensure cheerful effect and good reflection 
of light, or where necessary, to produce an 
impression of repose ; (b) use of unglazed 
surfaces BO as to avoid inconvenient 
reflections of light-sources, causing ^larc ? 

(2) Lighting <>j Hospital Wards. 

What special precautions should be 
observed in regard to the lighting of 
hospital wards, especially with a view to 
(a) shading and locating lights in such a 

manner as to afford sufficient illuminat ion 
but not give rise to glare in the eyes of 
patients lying in bed (either from lamps 
immediately above them or situated on 
the opposite side of the ward) : (b) 
dimming or alternative methods of lighting 
to enable lighting to he reduced to the 
necessary minimum at night. What 
degree of general illumination, in foot- 
candles irrespective of local lighting 
from plugs, etc. should he provided in 
the ward \ 

(3) Lighting of Operating Tables. 

Are any data available <>n the intensity 
of illumination necessary for various kinds 
of operations, and would it he desirable to 
tabulate specified values as a guide to 
practice in 'his reaped j flow can in- 
convenient shadows from the person of 
the operating surgeon best be avoided \ 
What precautions are usual to avoid 
harbouring of dust by fittings above 
the table ? 

- Do you consider that average daylight 
is preferable to good artificial light 
for operating work ! Assuming that 
" artificial daylight " (i.e., an illuminant 
corrected so as to have the same colour 

as daylight, and of sufficiently high 
intensity) could be economically obtained, 
would this be preferable to daylight ? 

(1) Special Inspection Lumps. 

What problems have you met in con- 
nection with the design of filaments of 
lamps, and the arrangement of inspection 
lamp.-, especially those with -mall hulls 
used for the inspection of internal organs, 

etc. What methods are best adapted to 
securing (a) sufficient illumination : (b) 
freedom from uneven brightness or 
" striatums," and (c) elimination of undue 
heating at the point where light is applied 1 
What special difficulties, if any. have you 
met with in obtaining suitable focusing 
lamps for ophthalmic work '. 

(.*)) Microscope Illumination. 

What is the best method of illuminating 
microscopes '. What data are available 
regarding (a) the necessary intensity of 
illumination on the slide and (b) the colour 
of light most favourable to the best 
definition ! 

(6) Illumination "J ( 'oloured Objects. 

What, in your experience, are the fields 
of work where correcl appearance of 
coloured objects is most essential [e.g., 
in examining rashes or affections of the 
skin, viewing internal organs, and in 
conducting operations, examining teeth, 
or in bacteriological work) ? Do you 
consider thai in such cases a device giving 
" artificial daylight" would prove useful ? 

(7) The Lighting <>f Pathological Museums. 

Information regarding the best arrange- 
ment of lamps for illuminating the contents 
of show-cases, the use of artificial day- 
light to obtain correcl colour-values, and 
other problems met with in the lighting of 
pathological museums would be welcome. 

(8) The Lighting of Dispensaries. 

Information is needed on the best 
methods of lighting Dispensaries, bearing 
in mind the scrupulous accuracy necessary 
in weighing out small quantities of material, 
the high speed at which such operations 
are necessarily carried out, and the fact 
that careful discrimination between 
colours is often important, 




By John Darch. 

(Introduction to the Joint Discussion arranged by the Illuminating Engineering Society in con- 
junction with the Royal Society of Medicine [Sections of Surgery and Ophthalmology], 
which took place at the House of the Royal Society of Arts, 18, John Street, Adelphi, London, 
W.G., at 8 p.m., on Thursday, April 27th, 1922.) 

In opening a discussion on Hospital 
Lighting, I hope that the remarks that 
time will permit me to make will elicit 
many practical and valuable suggestions 
from experienced surgeons and others 

While one cannot but feel the greatest 
a 1 miration for the service and equipment 
of the modern hospital, it must be said 

any material departure from Nature's 
principles of illumination must give 
trouble. There should be no glare from 
visible light sources, reflections or glaring 
glassware (Fig. 1). It would be unpleasant 
to the nurses or doctors, but it may occa- 
sion real distress to the sick, particularly 
when the glare enters the lower part of 
the eye, so much the more likely with the 

Fig. 1. — Examples of Glare found in Hospital Wards. 

that their excellence is marred by 
systems of artificial lighting that remind 
one of Miss Nightingale's trenchant 
observation that " the very first require- 
ment in a hospital is that it should do 
the. sick no harm.'' 
Let us first look at 


In designing an installation, whether 
of electricity, gas or other illuminant. it 
should always be remembered that the 
human eye has been evolved under untold 
ages of Nature's environment and that 

ward patient. On the other hand, 
insufficient light is also injurious. 1 have 
seen patients straining their eyes and 
twisting their necks and bodies in the 
endeavour to read by insufficient and 
badly-placed lights. Many wards have 
no patients' lights. 

The characteristic of ward lighting 
should be one that is quiet and pleasing. 
This can best be obtained by a system 
of {jieneral lighting combined with local 
lighting (Fig. 2). The general lighting need 
not be great — anything from a half to one 
foot-candle, according to the colour of 



the room, but it must be well diffused and 
without glare. It might be had by 
pendants of either indirect lighting with 
dishes of a quietly coloured and dense 
translucency not passing more than ± 
candlepower per sq. inch ; or by a ring 
screen of coloured china or silk of size 
and form just to conceal the lamps. In 
either case they should spread the light 
evenly over the ceilings and friezes. 

With this quiet and inoffensive general 
lighting each patient should be provided 
with his own local light giving him 3 

more easily cleaned, would be a semi- 
circular screen of the same material and 
colour, as shown in Fig. 2. 

Local lighting is also necessary on the 
sisters' and nurses' tables. Each should 
have one or more well-shaded table lamps 
adjustable so as to give an average of 
4 foot-candles, with deep rose silk 
flounces with white lining that would 
thoroughly screen the lamps and give a 
cheerful touch of colour to the room. 

Night light is of course necessary, and 
nothing is more soothing than a quite 

Patients' Lights 

for General Lighting 

Lamp coraoW S«*»cirtulor 

Ring Screen 

Indirect Lignh 

in dark Translucent Jish 

■ ■ //////////////y/////m^^ 

rtfr 2 " 


-Ward Lighting. 

foot-candles on his book, and under his 
or his nurse's control and for use only 
when he wants it. This may be on a 
short smooth bracket, set close back to 
the wall, so as not to be in view of the 
patient. It should not be in the centre 
of the bed head, as is usual, but about 
15 inches to the patient's left to avoid heat 
on his head and gloss on his book. It 
should illumine the patient's chart and 
be useful for the nurse or doctor. Afl 
this lamp should offend no one else, it 
should be fully recessed in a dark green 
shade ; or an alternative, which could be 

indirect light. A small lamp could quite 
well be used in one or more of the general 
lighting units, but it should be on a 
separate circuit. 

The decoration of the ward is an 
important factor in its illumination. 
Although ward ceilings and walls are 
frequently to be found varnished, there 
should be no gloss above the dado as 
any success in avoiding glare is usually 
frustrated by seeing all the lamps 
mirrored in ceilings and walls. 

The ceilings and friezes should be 
white. I am aware that bed-ridden 



patients' eyes are directed upwards, but 
this will be no discomfort if the lighting 
is arranged as I have suggested. The 
walls below are better of a quiet and 
restful colour of medium strength, darker 
or lighter, according to window space 
and aspect. The dado should be dark, as 
it is of little value in illumination and 
the eye needs rest. 
We now turn to 


With all the ingenuity that has been 
expended on the illumination of the 
operating table there seems to have been 
but a partial success. The surgeon is 

Fig. 3. — Comparative Sky-Intensities and 
Angles of Sunlight, also Window Intensities. 

still worried by the annoyance of trouble- 
some lighting ; of the shadow of his own 
head and hands if there be not an 
intolerable heat and glare. Occasionally 
he meets with light that is insufficient or 
bad in direction. These imperfections 
are confessed by the frequent recourse to 
the hand lamp when not otherwise 

Whatever arrangements are made, the 
highest possible degree of asepsis is of 
vital importance. If I mention the fact 
that I have seen fittings suspended over 
the table thickly coated with dust, it is 
only to point out that the scrupulous 
cleanliness usually exercised might, at 
times, be relaxed when an accidental 
knock would bring down a shower of 
dust. For that reason alone, no fittings 
should be placed or placeable over the 

operating table ; though, as a matter of 
fact, they generally are. I should, 
however, add that such fittings are usually 
to be found clean, smooth and easily 

Now the ideal light for major and 
general operations would be that found 
quite away in the open, under a clouded 
sky ; and it seems to me that our effort 
should be to obtain that same lighting 
as nearly as possible in the operating- 
room both day and night. Let us first 
consider its 

Natural Lighting. — For this purpose 
the position of the room is of great 

about 2 ft dia. 

Fig. 4. — Usual Types of Operating Lights. 

importance. A surgical ward unit in- 
cludes its operating room, and some 
authorities insist that it shall adjoin the 
ward to which it belongs. This fre- 
quently militates against good lighting. 
But I am with those who are convinced 
that the general operating rooms should 
be situated where the best light is 
obtainable ; and that, in most cases, is 
on a top floor,, to which a lift gives easy 
access from any ward. There are also 
economies in working several operating 
rooms together. These remarks do not 
apply to those of gynaecological, throat 
and some other departments. 

It should be observed that the sky is not 
equally luminous. I submit a diagram 
(Fig. 3) showing its relative brightness 
at different angles. The brightest portion 



is at the zenith and the mean is at 60° 
from the table. The diagram also shows 
how little enters a window even when 
there is no obstruction opposite. It also 
shows the summer elevation of the sun 
and how it governs the form of the roof. 
(Oi demands a sunscreen, as in Fig. 5.) 
One should secure the greatest possible 
angular expanse of glass without admit- 
ting direct sunlight and by extending 
it nearly the length of the room. 

The glass should be that which is 
clearesl and easiest cleaned; thatisto 
plain or, preferably, a clear smooth fluted 
kind. Rough ribbed oi ground glass 

obstructs lighl and holds dirt. The lower 
part of front to 6 ft. high may be of fine 

the shadow of one's hand on the work; 
and vision is easier in a diffused light. 

3. No exposed light sources should 
exist within the field of vision, although 
they commonly do. 

1. The colour of the light should be as 
white as possible, for correct colour 
estimates are sometimes of importance. 

5. The light must be uniform and 
steady ; even slow alternating current 
periods may irritate the Burgeon's ey< 

G. Finally, asepsis must be a primary 
consideration, and no fittings that will 
collect or disseminate dust should be 

Section Outside Elevation 

Km. 5.— Artificial Lighting from the Outside. 

ground glass to avoid distraction, and 
w it h sashes to open lor perflation. 

The ceilings and wall surfaces should 
lie white, smooth and washable. A grey 
or green dado would afford some relief 

to the eye without affecting the light. 

The anaesthetic and recovery rooms, 
also t he preparation and sterilising rooms, 
need a good light, but tall windows 
Should meet t he case. 

In dealing with 

Artificial Lighting, one should still 
keep in mind our ideal open-air illumin- 
ation, which will lead us to the best 
conditions of artificial lighting, i.e. : — 

1 . The illumination should be abundant 
— not less than 25 foot-candles. 

2. Tin 1 light should be so thoroughly 
diffused that it would be difficult to get 

I have seen some curious contrivances 
to solve the problem of lighting the 
operating table, Imt I will only say that 
the more usual devices vary from a single 
lamp under an ordinary opal reflector to 
a large cluster under a polished metal or 
silvered glass reflector (see Fig. 1). Some 
are movable on cords and pulleys, some 
telescoped, others fixed, which is better for 
dust. In nearly all cases they hang or are 
drawti directly over the table, some being 
on the end of a smooth long swing-arm 
on the wall or a pillar. In this position 
they direct a strong light into the incision, 
but that light is from one direction only, 
and in such a light true perception is 
always difficult. The surgeon is also 
bothered with the shadow of his own head 
and hands, and intricate and careful 
work is often made distressing by the 



Fig. 6. — Lighting Operating Table by Converging Rays from Mirrors (Prof, Seidentopf). 

Fig. 7. — Seidentopf System of Lighting Operating Tables showing direction of rays. 



intolerable heat on his head. The surgeon 
can, of course, always use an electric fore- 
head light, but one expects that to be 
necessary only in special circumstances, 
as the trailing rubber tube is incon- 

If the class of light in Fig. 4 be used, 
three or four of them placed obliquely to 
the table would save both the heat and 
the shadows, and give a more diffused 
and useful light on the work. 

An operating room should be clear of 
everything that can be possibly dis- 
pensed with, and there is no reason why 
it should not be entirely clear of lighting 
fittings. The best arrangement, in my 
opinion, and that best fulfilling the 

of the units are adjustable and may, 
if desired, be drawn aside entirely during 
the day. 

No other lights would be required, and 
even the pilot light might be kept in one 
of the reflectors and shed a sufficient 
light all over the room, or a concealed 
light used, as Fig. 9. 

Another method more in favour abroad 
than here is that of projected beams of 
light converging on the table from 
several points. 

I will first mention Prof. Seidentopf's 
invention, particulars of which Messrs. 
Korting & Mathieson sent me by the 
good offices of our friend, Mr. Justus 
Eck. Everything, excepting the light, is 

Fig. 8. — Plan showing Table lit by Project or Tubes. 

conditions I have laid down is to light 
the room entirely from the outside (see 
Fig. 5). Such a daylight arrangement 
as I have described would afford every 
facility for four or more clusters of 
powerful gasfilled lamps enclosed in 
waterproof parabolic reflector cases and 
give a light of 25 foot-candles or more 
on the table and a diffused light through- 
out the room. 

Arc lamps are not in favour now, but 
I have seen nothing better for this pur- 
pose than some white flame arcs we had 
before the war ; they were steady and 
silent, and gave the nearest approach to 
daylight that I have seen in any lamp. 
The arrangement I show provides for 
access on the outside for cleaning and 
trimming, and in either case the position 

kept outside, but there are a number of 
mirrors in the room to be kept clean. 
Fig. 6 is a picture of a theatre. A power- 
ful arc light is projected through a hole 
from an adjoining room to a bunch of 
mirrors opposite : thence it is dire, ted 
to other mirrors, set round the room, by 
which the light is converged from several 
directions to the table. 

Fig. 7 shows a room with a flat 
ceiling, carrying out the same idea. 
In this case the beams of light which, of 
course, are not really visible, are painted 
on the photograph to show t heii direction. 

Convergence of light on the table may 
be carried out in a simpler method In- 
fixing, say, four to six projector tubes, 
each containing a . (i()-watt gasfilled lamp 
and parabolic reflector, on adjustable 



brackets fixed to ceiling or cornice, as in 
Fig. 8. With this a general light will be 
required, which could be placed in a 
hemispherical glass enclosure on the 
ceiling. Any local wall lighting required 
could be by concealed lamps in a glass 
panel quite flush with the wall and 
accessible from the rear or front (Fig. 9). 

The same idea has been combined with 
general lighting in Marshall's operating 
pendant (Fig. 10) and is used in several 
hospitals. Beams of light converge to the 
table below from four Xernst glowers 
in tubes with lenses, but the arms are 
jointed so that the projectors can be 
concentrated in one direction. 

I need hardly mention that in all cases 
wall plugs are necessary for hand or 
standard lamps or any other clinical 
light. The trailing wires are always a 
nuisance, but it may be largely obviated 
by having the plug in the floor near the 
table, or, as in the London Hospital, in 
suspended service boxes (Fig. 10), which 
provide plugs respectively for hand lamps, 
standard projector lamps and emergency 
lamps, also cautery plugs and plugs for 
mechanical surgery as sawing and drilling. 

With regard to the 
preparation and othei 
rooms, I have time 
only to say that they 
should have, firstly, 
a modest general light 
well above sight line, 
and, secondly, local 
lighting to the sinks 
and sterilisers. 

There is another 
class of operating room 
found in many general 
hospitals having flat 
ordinary ceilings, and 
for daylight depend- 
ing upon a large tall 
window or sometimes 
a bay window. Indi- 
rect artificial lighting- 
is best for these with 
a white enamelled 
ceiling and frieze, as 
distemper gets loose 
and falls. There should 
be four reflector dishes 

Ceiling hve! 

General bahhnq when 
Oft' ~Room not in use 

Local VtqttinyjoT Smh Af- 

Fig. 9. — Concealed 
Lighting in Recesses. 

containing two or 

more powerful half-watt lamps and 

Fig. 10. — Marshall's Operating Pendant, with Nernst Projector Tubes, London Hospital. 



covered with clear glass for easy cleaning 
as shown in Fig. I I. These should yield 
25 foot-candles of a beautifully diffused 
lighl mi the table. 

Direct lighting might be made quite 
serviceable if kepi on the ceiling, with 
four or six hemispherical glass enclosures, 
hut it will not bi and diffusive 

as the indirect light. If there is a room 
0] space over the ceiling that would 
admit of access to these lamps, so much 
the better. 

In eithei case no other lighting would 
be necessary, so t here would be less chance 
of collecting dust. Even the pilot light 
could be m one of the glass enclosures. 

Provision musl be made for Emergency 
Lighting, hut risks of failure are no 

Dirtcf Ceiling Lighh 

Tig. 11. — In Operating Rooms with Ordinary 

( '« ■ i I I 1 1 J s . 

greatly reduced that to encumbei the 
room with alternative fittings (and each 

one is a dust trap) would be the gn 
evil. The first precaution should be to 
place one half of the lamps on an entirely 
separate circuit ; this would provide 
against the more likely risks. The second 
should be an electricity accumulator 
placed in another room large enough to 
maintain two or three 50-candlepower 
hand lamps for several hours. 

The question has arisen whether 
Artificial Daylight, used for textile colour 
matching, would be of service for clinical 
or surgical purposes. There can be little 
doubt of its usefulness if a suitable lamp 
with sufficient intensity is forthcoming. 
But there lies t he difficulty. The day- 
light lamps thai I have seen would be 
too feeble and clumsy for surgical use, 
and hardly to be considered dustproof. 
There is more prospect in daylight glass, 

and though we may not at present be 
able to get the abundance of light 

necessary for the operating room, day- 
light hand lamps might be usefully taken 
to the bedside or the operating table. 

May I close with just a word for 
the Dispenser, on whom so much depends 
while he is turning out hundreds of 
bottles daily. I have seen dispens 
badly lighted naturally and worse arti- 
ficially, and it would be but a small 
matter to saw the eye strain of reading 
graduated glass measures on a patchwork 
background of bottles and ensure greater 
accuracy if a small, plain, white and well- 
lit SCIeen Were placed where required, 

one to each man. The manner of their 

Fn . 12. — One of several arrangements 
of white screens to aid in Dispensary. 

adaptation and use would 1"' as manifold 
as the circumstances vary, but one 
illustration. Fig. 12, will show how to 
utilise an elusive streak of light. 

I must leave the consideration of halls, 
stairs, corridors and general service rooms, 
excepting to say that low drooping 
electroliers or gasoliers and spreading 
brackets are unsuitable to a hospital — 
even in the chapel or the governors" room. 
Direct lighting if used should be from 
the ceiling, and bracket lights should be 
protected from the eyes by a dense but 
narrow semicircular screen in which little 
light would be lost to the room. 

I hope that the question of the use of 
light in the gynaecological, throat, ear and 
eye departments will not be overlooked 
in the discussion as I have not had time 
to deal with them. 





Mr. C. C. Choyce said that the lighting 

of an operating theatre resolved itself 
into three necessities, viz., a good, diffuse 
general light, a special light over the 
table, and a handlight. If possible the 
handlight should come from a plug 
fitting into the floor, near the operating 
table ; wallplugs involved the passage 
of cable across the operating theatre ; 
plugs on a fitting above the table involved 
the danger of shaking down dust at each 
movement. But the drawback to the 
floor plug was that water was apt to get 
into the socket when the floor was washed. 
If some water-tight trap could be designed 
to take the plug, quite close to the table, 
it would be very advantageous. 

As regards the method of lighting, he 
thought that the main requirements from 
the surgeon's standpoint were : (a) mul- 
tiple origins of light, whether direct or 
by means of mirrors, to avoid the casting 
of inconvenient shadows by his hands, 
etc., on his field of work, and (b) coolness 
in the region of his head. 

For gynaecologists and people operating 
on the pelvis, it would be convenient to 
have two horizontal convergent rays of 
light coming from two wall lamps sunk 
into recesses in the wall, about 4 feet 
above the floor. 

The suggestion of the last speaker that 
the lights should be kept outside the 
operating room seemed sound, but in the 
case of high rooms there might be difficulty 
in obtaining the requisite illumination 
with reasonable economy ; and if tin' 
lighting units were situated outside the 
exterior wall, they should, of course, be 

The colouring of walls and floor in a 
theatre were, he thought, important, and 
he advocated a dull dark olive green for 
floor and walls up to eye-height. He re- 
called Professor Carrel's theatre in the 
Rockefeller Institute in New York, which 
was entirely black ; this convinced him 
of the advisability of dark floors, but he 
thought black unnecessarily funereal. 

Mr. W. T. Holmes Spicer said that 
good lighting was particularly essential 

in ophthalmic work, which involved the 
most delicate operations in all surgery. 
For work of this kind it was not desirable 
that light should be too much diffused ; 
extreme diffusion was not favourable to 
exact definition, as the surgeon required 
definite shadows. All glare should be 
absent, and reflections of light should be 
avoided, except those arising in the eye 
under examination. 

Generally speaking, in ophthalmic oper- 
ations it was desirable to concentrate the 
light on the eye, and leave the remainder 
of the room in subdued light so as to get 
the eyes of the operator adapted for 
darkness as far as possible. He recalled 
that as far back as 1893, when he was 
staying with Snellen of Utrecht, the 
latter had adopted the principle of 
working in a darkened room. An arrange- 
ment was made whereby the individual 
panes of the one exposed window could 
be uncovered at will, so that the operator 
had a beam of light under complete 
control falling on the eye. Snellen 
claimed that much more acute vision was 
possible in these circumstances, and he, 
the speaker, thought that the general 
principle was now accepted as best in 
eye operations. 

Mr. Conrad Beck said that he had 
been asked to make some remarks on 
the provision of illumination for micro- 
scopes used for medical purposes. The 
question was really limited to high powers 
as low power microscopes were used 
chiefly for preliminary and rough examin- 
ations of secondary importance. 

In viewing objects with high power 
microscopes there were certain contin- 
gencies to be borne in mind. Amongst 
these might be mentioned : — 

(a) It may be necessary to use colour- 
filters which materially reduced the 
intensity of the light. 

(b) Very dense specimens may have 
to be examined which likewise involves 
loss of light. 

(c) Sometimes it is necessary to illumin- 
ate an object on a dark ground and to 



rclv on the small proportion of light 
which the object is capable of reflecting. 

(d) It may be required to direct a very 
small and almost parallel beam of light 
on the object. 

All these contingencies demand that 
the available intensity <>/ light must be 
great. Moreover, the magnifying power 
of a microscope is commonly expressed 

as a linear factor. Thus, if an object is 
examined with a microscope of magnify- 
ing power loo, the image is spread over 
an area L0,000 times its actual size, and 
the illuminat ion is reduced proportionally. 
Mr. Beck pointed out thai a change in 
magnifying power thus demanded a 
difference in illumination. When a semi- 
transparent object was being examined 
the actual intensity required was less 
than might be supposed, because in 
ordinary circumstances one examined 
such objects against a relatively mildly 
luminous background. Thus, if one tried 
to make out the pattern of a lady's veil 
against a bright sky the effect would be 
inoonveniently dazzling. On the other 
hand, for dark ground illumination one 
needed an intensity which it would be 
quite impossible to use for transparent 
objects, and if colour filters were used 
the intensity provided must again be 

much greater owing to the huge amount 

of light they absorbed. One was thus led 
to the second primary requirement in 
microscope illumination, often insuffi- 
ciently realised, namely, that the intensity 

provided must be capable of wide variation. 
This variable illumination was best 
obtained by the use of a pair of adjust- 
able neutral dark wedges, through which 
light Erom an intense source was allowed 
to pass on its way to the object illum- 

A further consideration arose in con- 
nection with the manipulation of the 
microscope. Every microscope object 
glass had a particular aperture, corres- 
ponding with the magnifying power. It 
must sometimes collect from each point 
of the object a cone of light which will 
fill the aperture, in order to- reach the 
full power of resolution or definition. In 
other cases, where this large cone of light 
would not give the necessary contrast to 
a very transparent object to render it 
visible, a narrow cone of light must be 

used, and the full resolution sacrificed. 
Consequently microscopes were fitted 

with a series of lenses known as " sub- 
Stage condense s " to direct the light as 
a wide angle cone focused through the 
object, the angle of this cone of li^ht 
being regulated by an iris diaphragm. 
Opening the aperture would cause an 
increase in intensity, which might have 
to be compensated by an adjustment of 
the neutral glass wedges, or other appro- 
priate device. 

A^ regards the nature of the source of 
light, an important consideration was 
that its area should not be too large ; 
otherwise there was apt to be reflection 
of light at the slip or cover glass, causing 
glare or " flooding -: which had the effect 
of producing a luminous veil which might 
even obliterate the image. Mr. Beck 
added that he had been making a series 
of experiments into the effects of such 
extraneous light and had found that 
they could be cured by confining the 
illumination to the exact part of the 
object under examination. From this 
standpoint daylight was probably the 
worst possible source of illumination for 
high power microscope work, owing to 
the diffused character of the light, and its 
relatively low intrinsic brightness (fre- 
quently not exceeding 2 candles per 
sq. in.) which no arrangement of mirrors 
or lenses could intensify. A paraffin 
lamp, with a brightness of 10 candle- 
power per sq. in., was sufficient for a 
great deal of work not involving colour 
filters. An incandescent gas mantle could 
be used without colour filters or for 
dark ground illumination. The tungsten 
vacuum electric lamp would be excellent 
if a suitable filament in the form of a coil 
\ in. diameter suitable for use on an 
ordinary lighting circuit could be devised. 
The " pointolite " 100 candlepower lamp 
was an ideal source where direct current 
was available. It had a brightness of 
12,000 candlepower per sq. in., and was 
sufficient for dark ground illumination 
with colour filters, and in fact met all 
ordinary requirements. Where a direct 
current supply was not available a thorium 
pastille, heated by a bunsen burner, was 
probably the best source. If a small and 
perfectly regulated arc lamp taking only 
2 — 5 amperes were available, this would 
also be excellent, but in his experience he 



had not found an arc lamp which com- 
pletely answered requirements for such 
work. The practice of using a ground or 
opal glass in front of an illuminant was 
thoroughly unsatisfactory, unless pro- 
vided with a diaphragm to reduce the size 
of the secondary source of light, as it gave 
rise to the glare and " flooding " effects 
referred to above. 

Mr. Beck pointed out that the intensity 
of light in the final image seen in the 
microscope should be almost dim, even 
though the light directed on the object 
might be very intense. Unduly great 
brilliancy of the actual image seen by the 
eye tended to impair the quality of the 
definition and might damage the ob- 
server's eyesight. He might, however, 
mention — as showing that continuous 
work with a microscope was not neces- 
sarily prejudicial to vision provided 
proper precautions were taken — that one 
of the staff of his firm had tested micro- 
scope object glasses for about five or six 
hours a day for fifty years without de- 
leterious effect on his eyes. He had 
always used a dim light and sat in a room 
with subdued general illumination. 

The colour of light that was best for 
microscope work depended on whether 
stained preparations were used. Special 
colour filters were useful in differentiatiim 
particular stained structure. But if 
colour-differentiation was not required a 
monochromatic green (about 500 A.U.) 
would give the highest resolving power, 
combined with the most comfortable 
colour to work with. Most people found 
that a hue located much further towards 
the violet end of the spectrum, although 
giving better resolution, was irritating to 
the eyes. The question thus resolved 
itself into a compromise between the 
wavelengths respectively best adapted to 
high resolving power and comfort of 
vision. The Wratten B and H screens 
were both excellent ; personally he pre- 
ferred to work with the B screen. 

Mr. J. B. Reiner referred to some of 
the optical problems met with in design- 
ing portable lamps for hospital work and 
mentioned that one of the chief diffi- 
culties was to obtain lamps of 100 to 240 
volts having a compact filament in one 
plane, similar to the available 30 volt 
type, which provide a distinctly better pro- 

jection illumination than that obtainable 
with the present high voltage types. A 
surgeon requires a circle of light of con- 
siderable brightness, uniform illumination, 
and as free as possible from striatum due 
to images of the filament. The difficult v 
might be overcome to some extent by 
using larger objectives so as to include 
the large filament of the higher voltage 
lamps, but this necessitates the apparatus 
being far more bulky ; another con- 
sideration was that, owing to the large 
amount of light not usefully employed 
through the optical system, the lamp 
was apt to get unduly hot. Lamps 
with a double tier filament are impos- 
sible for projection as the filament 
images cannot be eliminated. Mr. Reiner 
exhibited several lamps which he had 
designed specially to overcome these 
difficulties and also a form of lamp for 
operating work, the chief feature of 
which was that rays from a central lamp 
were collected and concentrated from 
three different directions by means of 
inclined mirrors. 

Mr. A. Wilson, speaking in the absence 
of Major Ashley Waller, illustrated the 
Seialytic Light, which had been found 
of great use by surgeons in hospitals, 
and had been designed by the French 
firm of optical and lighthouse engineers, 
Messrs. Barbier, Benard and Turenne. 
Designed during the war, these units 
had proved of considerable value and 
had, he believed, been installed in most 
of the chief London and Parisian hospi- 
tals, notably the Broccas hospital, the 
London, Middlesex and Charing Cross 
hospitals, the Mayo Institute in the 
United States, and in various hospitals 
under the War Office and the Admiralty. 

The apparatus consisted of an inverted 
aluminium saucer-shaped bowl, in the 
centre of which was fitted a cylindrical 
five-element dioptric lens. In the centre 
of this lens a 100 watt gasfilled lamp 
was commonly used. Around the inside 
rim of the saucer-shaped bowl were fitted 
thirty-nine silvered mirror reflectors, 
each set at a slightly different angle. 
The rays from the source of light, passing 
through the dioptric lens, were caught 
by the reflectors and then reflected 
in a cone to the converting point, 3 to 
3£ feet below the lamp — which in this 



case was the patient on the operating 
table. All the rays wore concentrated 
into an 18-inch diameter patch, and the 
intensity was of the order of 3,0(J0 

adji]flt«h!f > lampholHe 

L)|ht tbouf , 

39 in t 

•W» ublc \ 

Sectional Elevation. 

candlepower. As would be understood, 
if the surgeon was leaning over the 
operating table during an operation, a 
certain amount of light did not reach 
the table, but the rays that did do so 
overcame the shadows cast by the 
head and shoulders of the surgeon, and 
furnished a shadowless light, by which the 
surgeon could easily see to the bottom 
of a six-inch incision. 

Plan, looking up. 

At the base of the lamp was fitted a 
detachable and specially toughened heat 
screen, so that the objectionable heat, 
to which surgeons were subjected with 
the old form of operating light, was 

entirely eliminated. This screen also 
provided a means by which access could 
be obtained to the lens and mirrors 
for periodical cleaning. 

At the top of the lamp was fitted a 
special bayonet cap, so that, in the rare 
event of a lamp burning out, it could be. 
replaced by a new one in a very few 
seconds. A sliding tube was also pro- 
vided in this cap to allow for focusing 
of the lamp in the lens. 

Mr. F. C. Raphael, M.I.E.E., said that 
he had listened to the paper with a sense 
of relief. He had expected to be told 
that all his present practice was wrong ; 
but he found that nothing very new had 
been put forward, and certainly nothing 
in any sense revolutionary. He de- 
scribed briefly the fittings and methods 
of lighting which he employed in the 
hospitals with which he is connected. 
Indirect lighting, in his opinion, was 
most cheerless far too cheerless for 
a hospital. It imitated daylight, but 
with only a fraction of good daylight 
illumination, so that the room had 
the appearance as on a foggv day. 
Against indirect lighting there was also 
the question of cost for more current. 
In many hospitals the electric light and 
power bill already runs into four figures 
annually. Semi - indirect lighting was 
better, but the fittings collected too much 
dust for use in hospital ward lighting. 

The lamp described by Mr. Reiner 
had been tried in one of the operating 
theatres as a floor standard, and was 
an excellent thing, and a distinct im- 
provement on the Nernst burner and 
lens system originally used. He was 
glad that Mr. Reiner was producing a 
lamp which would operate on 200 volts. 
A little extra weight would not condemn 
it. Ample provision should be made for 
ventilation of the lantern, both to 
prevent the lantern itself getting too hot 
(particularly important in the case of 
hand examination lamps in wards, which 
might be laid down on beds) and to save 
lamp renewals. 

Indiscriminate use of gasfilled lamps 
frequently gave rise to patchy illumina- 
tion, and also waste by the users 
increasing the size of their lamps and 
using more of them to bring the mini- 
mum illumination nearer to that of the 

THE lLLr.MI\.\TIX<; KXCIXKER (junk 1922) 


maximum. They must be used with 
discrimination and the light properly 


Mr. Raphael regarded the Fullolite 
lamp as very satisfactory. The diffusion 
was very good and solved a great part 
of the difficulty of shading. Such lamps 
were popular at the largest hospital with 
which he was connected, and would 
doubtless be used very laigely if the lift- 
proved sufficient. He had inspected 
every method of lighting an operating 
theatre and had found that ordinary 
lamps or Fullolites on a simple but 
suitably designed fitting answered most 
purposes. The Zeiss method, with an 
arc lamp outside the room, the light 
from which was directed on to the table 
by numerous mirrors, had been employed 
at Middlesex Hospital, but the experience 
of an eminent surgeon connected with 
another hospital had been unsatisfactory. 
Apparently one suddenly encountered 
unexpected shadows. Outside lamps over 
a skylight were not a success. The 
method involved an enormous wattage 
for a given illumination on the table. 
A drawback with the Scialytic unit was 
that its extensive hood excluded day- 
light. Another objection was that it 
used only a single lamp, which might 
fail during an operation. The patch 
of light was also small and some surgeons 
asked for a radius larger than 18 inches 
or so. 

Dispensary lighting presented no diffi- 
culties with proper arrangement of points 
and fittings. It was important that the 
labels and markings on bottles should be 
well illuminated. 

Mr. J. W. Elliott exhibited some 
" Fullolite " lamps, the feature of which 
is the use of an opal glass bulb, whereby 
the filament of a gasfilled lamp is com- 
pletely screened from view and the light 
uniformly distributed. As these lamps 
are now manufactured for the lower 
wattages they are considered particularly 
suitable for use in hospital wards, with 
a view to avoiding glare. 

Another form of lamp exhibited, known 
as a " Night Light " lamp, also recom- 
mended for use in hospital wards, con- 
tained two filaments, one giving a normal 
candlepowei suited for ordinary use, the 
other a smaller filament giving a greatly 

reduced eandlepower, with correspond- 
ingly reduced consumption. By operating 
a switch either filament could be brought 
into operation and the illumination thus 
reduced to a suitably low value at a 
certain hour at night. 

Mr. W. J. Jones said he had listened 
very carefully to the remarks made by 
Mr. John Darch and was in full agreement 
with the comments which he had made 
concerning the lighting of hospitals. It 
had been his duty in the course of business 
to visit a very large number of hospitals 
in this country and some abroad, and it 
was quite obvious that the lighting of 

Type of dust-proof hospital unit. 

hospitals had not received the scientific 
treatment that it deserved. 

He, too, had frequently noted the bad 
method of lighting by means of brackets 
imperfectly shaded, and had experienced 
as a patient the inevitable discomfort. 

These brackets over the beds should 
be provided with adequate shades, and 
he was surprised to hear that Mr. Raphael 
considered the satin finished shade to be 

For some time past illuminating 
engineers had been considering the design 
of fittings which fulfilled the hygienic con- 
ditions for hospital use, which did not 



collect the dust and could be easily 
cleaned. With this view in mind the 
English Electric and Siemens Supplies 
Co., Ltd., had recently introduced a unit 
type fitting which had all the advantages 
of the semi-indirect bowl without its 
disadvantage as a dust trap. The fitting 
was provided with an opal glass bowl to 
which was joined a clear glass top. The 
fitting could be adequately cleaned with- 
out handling the lamp itself. The polar 
curve of distribution was quite satisfac- 
tory, and this fitting should prove of great 
service for the general lighting of wards, 
corridors, and in some cases operating 

He was familiar with the various 
methods of lighting operating theatres 
which had been mentioned by Mr. Darch, 
and would mention that he had usually 
found a general illumination of approxi- 
mately 10 foot-candhs with a concen- 
t rated light of at least 20 foot-candles on 
the table itself. 

He was quite certain that lights pro- 
vided locally over the top of the table 
were the best solution of the difficulty. 
In nearly every instance of operating 
theatre lighting with which he had come 
in contact, a floor standard was provided 
that was capable of giving powerful local 

Not only was it common to find dis- 
pensaries placed in dismal surroundings, 
but it was often found that the X-ray 
departments, too, were badly located. 
Quite often the installation was placed in 
the basement with little natural daylight. 
The access of daylight provided in the 
majority of cases was grossly inadequate, 
and only those who have had occasion to 
work in such departments know how 
necessary it is to have cheerful and 
hygienic lighting at all times. The 
inevitable periods when light must be 
excluded to screen satisfactorily patients 
produced a peculiar depressing and 
irritating effect. 

One of the difficulties that he had 
experienced with such installations was 
the continual failure of metal filament 
lamps when in the vicinity of. overhead 
high tension leads from the coil or trans- 
former. These leads, which might be at 
a potential of anything between 100,000 
and 300,000 volts, exerted an extremely 
powerful electrostatic field, which led to 

the fracturing of the lamp filament. By 
surrounding the lamp with a wire guard 
almost the whole of the trouble could be 

The firm with which he was associated 
had recently introduced gasfilled lamps 
with " Daylight Bulbs." These tinted 
bulbs possess the ability to transmit 
selectively the radiation from the filament, 
so that the resultant light approached 
that of average daylight. Natural day- 
light was by no means constant in its 
qualities, and the advent of the artificial 
daylight lamp should enable accurate 
comparisons to be made. 

It would appeal that such a light would 
prove of very great value in the exam- 
ination of rashes, prints and organisms. 

One of the London hospitals was 
installing these lamps in the operating 
theatre and a number were being used 
for examination purposes in isolation 
hospitals ; some useful information con- 
cerning their value for this work should 
be available in the near future. 

In conclusion, the greatest care should 
be taken to see that the electrical 
arrangements in hospitals were carefully 
planned in order that there might be 
little chance of failure of light in impor- 
tant situations, and these arrangements 
should be left in the hands of capable 
consulting electrical engineers. 

Mr. E. W. Johnstox mentioned that 
the practical application of illumination 
to hospitals, where hygiene must be the 
first consideration, necessarily differed 
considerably from the ideal. There were 
one or two clear illustrations of this in the 
paper and the remarks of previous 

Regarding theatre lighting Mr. John- 
ston said that he had in use some 
parabolic reflectors on swinging arms 
but these were not too successful. He 
also had in use " Fullolite " lamps, but 
arranged "five of diamonds" fashion on a 
frame measuring five feet by three feet 
suspended from a swinging arm, which 
was more satisfactory ; and failing 
something better and simpler he would 
continue to favour this relatively cheap 

He wished to appeal to lamp manu- 
facturers to apply themselves to the 
design of both low and high voltage lamps 



with filaments arranged to show in one 
plane a small evenly illuminated field 
approaching as near as possible to a 
" point " source. The " pointolite " 
was ideal in this respect, but something 
less complicated and expensive was neces- 
sary, and if it could be evolved it would 
have many applications in hospital work. 
Mr. Johnston considered that there 
were few buildings which contained so 
many interesting and varied problems 
for the illuminating engineer than a 
modern hospital. 

Mr. L. Gaster, in thanking Mr. Darch 
for his introductory paper, remarked that 
the discussion had shown that there was 
room for much further research on the 
Use of Light in Hospitals. He also 
wished to thank those who had con- 
tributed to the interest of the proceedings 
by arranging exhibits of apparatus. A 
list of queries, which was not exhaustive 
but would serve to indicate some of the 
points on which fuller information was 
needed, had been prepared for circulation 
amongst hospital surgeons and others 
interested and would be published in the 
journal in due course. 

Mr. Gaster mentioned that he had 
recently been taking part in the work of 
a small committee, formed by one of the 
leading ophthalmic hospitals, with which 
the President was associated. They had 
been specially concerned with the design 
of portable lamps for ophthalmic ex- 
aminations, in which they hoped to make 
some improvements. He thought that 
the procedure of this hospital, in forming 
a small local committee to study various 
lighting problems, might well be adopted 
by others. 

It was suggested that general in- 
vestigations on hospital lighting might 
be undertaken by a small joint com- 
mittee, on which members of the 
Illuminating Engineering Society and 
leading ophthalmological and medical 
bodies should be represented. The work 
of such a committee should be useful in 
bringing about agreement on general 
principles, and making recommendations 
which would serve as a guide to those in 
charge of hospitals. 

Major J. P. Ashley Waller (com- 
municated) : With regard to the shadow 

cast by the hood of the Scialytic Light, 
where this fitting is hung under a sky- 
light, most hospitals like this light with 
an adjustable suspension and this sus- 
pension allows the hood to be turned up 
on edge when not in use. In this 
position no appreciable shadow is cast 
on the operating table. 

With regard to lamp failure, it may be 
noted that the great feature of the 
Scialytic Light is the fact that it provides 
a very high candlepower with a lamp of 
very low wattage. My general ex- 
perience is that such lamps scarcely ever 
burn out, but only gradually become less 
and less efficient as their life extends. 
Further, in the rare event of the lamp 
itself failing, very quick means exist for 
changing the lamp, and, of course, if 
the light fails through lack of current, 
this would apply to any form of electric 
lighting which might be used. I may 
state, however, that it is quite easy to 
fit a battery in connection with the 
lamp in the Scialytic Light so that if the 
main current does fail, the battery can 
be immediately switched on and the 
light maintained. 

Surgeons requiring an illuminated area 
greater than 18 ins. in diameter are, we 
find, in a very small minority, and it is 
always possible to construct a special 
type Scialytic for them at a small extra 

(At the conclusion of the Discussion 
some special forms of lamps for medical 
work were exhibited by Messrs. Mayer 
and Phelps. These included the 
" Chiron " lamp, which is regarded as 
the standard lamp for the consulting 
room of the surgeon and specialist. 
This is fitted with a gasfilled lamp 
semi-obscured vertically and with a plane 
convex lens to give parallel rays. It is 
stated to throw a clear disc of light 
without any image of the filament, and 
is of particular use in examining the 
throat, nose and ear. Similar equipment 
fitted with " daylight " lamps and with 
a coloured screen to illuminate the field 
in natural colours were also shown. An 
iris diaphragm is fitted for ophthalmic 
work. Other exhibits by Messrs. Mayer 
and Phelps included a selection of 
instruments for examining the various 
cavities of the body electrically ilium- 



inated, such as laryngoscopes, pharyn- 
goscopes, oesophagoscopes, etc. By means 
of such instruments, it is claimed., parts 

of the body can be examined and treated 
that were previously inaccessible.) 

Mr. J. Dabch, in reply, states : I was 
pleased to note how much Mr. Choyce's 
views on lighting operating theatres 

accorded with those 1 laid before the 
meeting. He, however, questioned the 
possibility of obtaining, economically, 
sufficient illumination from outside light- 
ing on account of the distance of the 
lamps. If the building had to be con- 
structed there is little need for the ■. 
roof to exceed an average of 1 1 ft. from 
the floor in the case of operating rot 
and say 13 ft. in the case of theatres. 
Even if the lam) is were 12 ft. from the 
table, six units with parabolic reflectors, 
as suggested, should easily direct an 
illumination of 25 foot-candles. And as 
to cost, the lamps need only be in full 
use during the comparatively short time 
occupied by the operation. 1 am hoping, 
however, for a revival of the white flame 
arc lamp, which, with perfect carbons 
and effective mechanism, should In- 
steady and dependable, and would yield 
an abundance of uniform light, approach- 
ing daylight, at one-fourth of the cost of 
electricity in incandescent lamps. 

Mr. Choyce, in speaking of the import- 
ance of the colouring of the walls of a 
theatre, referred to the Rockefeller In- 
stitute where the walls were black. 
This is to emphasise, by contrast, the 
lighting on the table ; but while it has 
that effect, it entirely prevents diffusion, 
so necessary to correct observation, 
besides " eating up " about 40 per cent. 
of the light. On the other hand, a 
dazzling reflection from all points is 
equally wasteful, because the result is a 
contraction of the pupil, which stops out 
much of the light. The best scheme of 
colouring would, as Mr. Choyce suggests, 
include quite a dark floor with a green or 
grey dado, 5 ft. high, but the upper walls 
and ceiling, if any, should be white. 
This arrangement, while relieving the 
eyes, would not reduce the light on the 

Mr. W. J. Jones seems to have fully 
recognised the bad lighting that is, un- 
fortunately, all too common in our 

modern hospital wards. It is to be 
regretted that so many hospital engineers 
do not appear to be equally impressed. 

I submitted an arrangement for clear 
glass covers to indirect lighting howls to 
the Royal Sanitary Institute ten years 
but I am glad to see that the firm 
Mr. .bmes mentions has recently taken to 
making them. I cannot, however, agree 
with him that the best place for an 
operating lighl is directly over the table, 
for the several reasons given in my 

Mr. Jones has expressed my own ex- 
perience as to the wretched position and 
lighting of some hospital dispensaries. If 
the architect cannot give the dispel 
all the daylight that their work demands, 
there should, at least, be a sufficiency of 
artificial lighting. It should consist of a 
moderate general lighting with local 
lighting to the shelves, so arranged that 
the label on every bottle is easily read- 
able by means of opaque shaded lamps, 
so fixed as to avoid "loss on the labels. 
Local well-shaded lamps should be pro- 
vided to the sinks and benches, and a 
white screen illuminated opal if re- 
quired to each dispenser to act as a 
background for reading glass measures. 
A lamp should also be placed inside the 
head of t be door to the poison cupboard. 

Mr. Raphael stated that be listened to 
my Paper " with a sense of relief," for he 
" had expected to be told that his present 
practice was wrong." Seeing that I was 
not aware which bospital be represented 
I could hardly have done so. But now 
there is little doubt about it. I noted 
that his advocacy of the lighting of a 
ward with satin finished glass shades over 
the beds was promptly condemned l>y 
Mr. W. J. Jones. Such lighting is an un- 
necessary cruelty to the helpless patient, 
for glass shades, either frosted, satin 
finished, prismatic or opal, are an in- 
sufficient protection. It is not the in- 
tensity of the light per se, so much as its 
violent contrast with its darker surround- 
ings that does the mischief. It has been 
stated by Prof. Weber more than 10 years 
ago, and endorsed more recently by a 
committee in America, that the safe limit 
of contrast is 100 to 1. Now Mr. 
Raphael's satin finished " shades " would 
probably yield a contrast running into 
thousands to one. 



INDEX, June, 1922 

Editorial. By L. Gaster 

^Humiliating Engineering Society— 

(Founded in London, 1909) 
Account of Meeting on April 27th 
Queries on " The Use of Light in Hospitals " 

The Use of Light in Hospitals. By John Darch 

Discussion — C. C. Choyce — W. T. Holmes Spicer — Conrad Beck — 
J. B. Reiner— A. Wilson— F. C. Raphael— J. W. Elliott— 
W. J. Jones — E. W. Johnston — L. Gaster — Major J. P. 

Ashley Waller— J. Darch (in reply) . . 

Reviews of Books 

Topical and Industrial Section 







Engineering Steels. By Leslie Aitchison, 
D.Met., B.Sc., M.I.A.E. (Macdonald 
and Evans, London, pp. 396, figs. 114. 
2 05. net.) 

In the introduction the Author refers 
to the developments that have taken 
place in high quality steels during the 
past two decades, and the need for exact 
specifications. A foreword by Professor 
W. C. Unwin remarks that in treating 
steels from the engineering standpoint a 
considerable amount of new ground is 
covered. The earlier chapters deal with 
steel melting processes, its casting, work- 
ing and heat treatment, after which the 
mechanical testing of steel is discussed 
in detail. Following this we have 
chapters devoted to special alloy steels, 
case-hardening and cold worked steels, 
etc. The book is printed in clear type 
on, good paper and the text is aided by 
a liberal use of illustrations, including a 
number of plates on art paper. Those at 
the end of the book illustrating varieties 
of steels in section ate particularly good. 

The Telescope. By Louis Bell. Ph.D. 
(McGfraw Hill Publishing Co.. Ltd.. 
London. 1922. pp. 287.) 

Dr. Louis Bell, whose name is familiar 
to our readers as a Past President of 
the Illuminating Engineering Society in 
the United States, embarks on a new field 
in this work on the telescope, in which 
he has assembled much scattered in- 

formation inaccessible to ordinary readers. 
The initial chapter on the evolution of 
the telescope makes interesting reading. 
Following this, Dr. Bell deals with the 
modern telescope, optical glass and its 
working, and mounting and accessories. 
The chapters on the care of and testing 
of telescopes and on " seeing and 
magnification," in which the effect of 
atmospheric conditions, apart from the 
limitations of optical apparatus, is dis- 
cussed, well deserve study. The paper 
and printing are excellent and the 
illustrations, both historical and technical, 
are clear and well executed. We com- 
mend this work to the notice of all 
interested in telescopic work, especially 
as it is some time since a work has 
appeared devoted primarily to this 

The South Western Railway Magazine 
{April, 1922). 

We have received from Mr. A. Cunning- 
ton, lighting engineer to the London and 
South Western Railway, a copy of the 
" South Western Railway Magazine " 
devoted to the new Waterloo station. 
The account is illustrated by many 
special photographs, some of them de- 
picting incidents during the recent visit 
of Her Majesty at the opening ceremony 
on March 21st. We notice that an 
account of the special floodlighting of 
I he Memorial Arch, recently described 
in this Journal, is included. 




— • • • • — 

[At the request of many of our readers we have extended the space devoted to 
this Section, and are open to receive for publication particulars of interesting 
installations, new developments in lamps, fixtures, and all kinds of apparatus connected 
with illumination. 

The contents of these pages, in which is included information supplied by the 
makers, will, it is hoped, serve as a guide to recent commercial developments, and we 
welcome the receipt of all bona-fide information relating thereto.] 


On Juno 9th a luncheon was given by 
Messrs. Allen Liversedge, Ltd., at the 
Hotel Cecil, followed by a film illustrating 
the manufacture and uses of dissolved 
acetylene. The idea of dealing with the 
matter by the aid of a cinematograph 
film was an enterprising step, and dis- 
solved acetylene lends itself well to this 
i real ment. 

The first pictures showed how the gas 
is produced and stored. After very care- 
ful purification the acetylene is dissolved 
in acetone and introduced into cylinders 
filled with kapok, a lighl and porous 
vegetable product from the Bast. Ap- 
proximately ten million of these fibres, 
the structure of which was illustrated 
under the microscope, are required to 
lill a space of 2 cubic feet. Acetone dis- 
solves 25 times its own volume of acetylene 
for every atmosphere of pressure (15 lb. 
per sq. in.). The maximum pressure of 
compression used in filling the cylinders 
is 225 II). per sq. in. A typical cylinder 
will contain 36 lb. of kapok, 36 lb. of 
acetone, and 200 cubic feet of acetylene, 
but a great variety of sizes is available. 

The whole process of making and 
purifying the gas, and subsequently 
storing it in cylinders, was shown on the 
film, the final stage being the driving off 
from the works of motor-lorries carrying 
cylinders to their destinations throughout 
the country. 

The varied uses of dissolved acetylene 
were next illustrated. One picture 
showed the difference in size (occasioned 
by the varied consumption of oxygen), 
of welding and cutting flames. The 
Bunsen flame used for brazing, soldering, 
lead-burning, etc., attains 4,600° F. But 

in the o\\ -acetylene flame used for 
welding and cutting 6,500° F. is attained. 
The process of metal cutting, in removing 
condemned ship plates, was shown, the 
progressive eating away of a line along 

the plate and its ultimate severance being 

clearly illustrated. Soldering, welding, 
brazing and other operations were like- 
wise depicted, and a very instructive 
study of the molten metal in the weld, as 
revealed by the ultra-rapid camera, was 

Dissolved acetylene has of course many 
other uses, it forms a convenient form 
of portable and emergency lighting, and 
proves very useful for motor-cars and 
motor-cycles. Perhaps one of the most 
pleasing pictures was that showing a 
motor-driven picnic party. When the 
party had arrived at their destination and 
set out the materials for tea, the tube of 
dissolved acetylene, ordinarily available 
for lighting, was removed from the car. 
It was rapidly connected to a small 
portable stove, which started the kettle 
boiling in a very short space of time. 
These acetylene stoves are very light and 
compact, one portable type being hardly 
larger than a girl's hand (illustrated on 
the film) and capable of being easily 
carried in the pocket. 

Sir William Noble, who has just 
retired from the position of Engineer-in- 
Chief to the Post Office, has accepted a 
seat on the Board of The General Electric 
Co., Ltd. We understand that Sir 
William Noble proposes to devote his 
attention mainly to the development of 
the Telephone and Wireless sections of 
this important manufacturing concern. 









illuminating Engineering society. 

Founded in London, 1909, 


Tel. No. Victoria 5215. 


The Fourteenth Annual Meeting of the Illuminating Engineering Society. 

From the outset the Illuminating Engineering Society has always 
been identified with the spirit of co-operation and it is satisfactory to 
note that the past session has afforded many instances of concerted effort 
with kindred bodies in dealing with subjects of mutual interest. The 
range of topics dealt with has been exceptionally wide, discussions on such 
subjects as " The Use of Light as an Aid to Aerial Navigation," " Recent 
Progress in Gas Lighting," " Industrial Lighting : Ideal Requirements 
and Practical Solutions," " The Lighting of Public Buildings," and " The 
L'se of Light in Hospitals " being included. The paper by Lieut. -Colonel 
Bland}* on " The L'se of Light in Aerial Navigation " was presented at 
a joint meeting with the Royal Aeronautical Society ; the discussion on 
" The Lighting of Public Buildings " was arranged jointly with the Royal 
Institute of British Architects ; and the discussion on " The L'se of Light 
in Hospitals " in co-operation with the Royal Society of Medicine. The 
wide scope of the Society's work was also referred to by all the speakers 
at the Annual Dinner of the Society held on February ioth. 

Many of the problems recently dealt with have involved consideration 
of the effect of light on the human eye, and this Society has been most 
fortunate to have for its President an eminent ophthalmic surgeon, Sir 
John Herbert Parsons, whose address at the Annual Meeting is reproduced 


in this issue (pp. 194-197). Sir John pointed out very aptly the limitations 
of theories based exclusively on physical observations, and showed how 
intimately illuminating engineering is concerned with the impressions of 
the senses and particularly those recorded by the eye. Physiological optics 
plays a great part in photometry, and there are many aspects of lighting, 
notably those concerned with the elimination of glare, where the help of 
the oculist is essential. The recent discussion on hospital lighting, again, 
showed how clearly necessary it is to enlist the help of the medical profession ; 
we should, for example, first ascertain from the surgeon what are the 
conditions of lighting he desires for different classes of operations, and then 
consider how these needs can best be met by the resources of illuminating 

There have been other instances of co-operation with other bodies, 
for example, with the London " Safety First " Council, and the British 
Industrial " Safety First " Association, which are mentioned in the Annual 
Report of the Council. A gratifying feature of the past year has been 
the resumption of activities of the International Illumination Commission, 
whose first technical session, already recorded in this Journal, should lead 
to useful results in the future. Another instance of international treatment 
of illumination is afforded by the attention being devoted to industrial 
lighting by the Section of Industrial Hygiene, operating under the League 
of Nations at Geneva, with which Dr. Carozzi, a valued corresponding 
member of the Society, is associated. 

There is thus every reason to be satisfied with the growing influence of 
the Society, and the constant extension of its field of work. We are also 
glad to note that the financial position of the Society has been a little 
improved by the new arrangements made in regard to fees for membership. 
But it is now generally agreed that the full extension and development of 
the Society's work demands a considerable further increase in revenue, such 
as might be derived from a substantially increased membership or from 
fuller co-operation on the part of the various industries or associations 
concerned with the lighting field. Increased revenue is particularly 
necessary to the proper carrying out of investigations by the various 
Committees of the Society. 

It is felt that the time is ripe for an effort to awaken interest in the 
work of the Society and add to its membership, and in the present issue 
we accordingly include a summary of the activities of the Society to date 
(pp. 203-218), accompanied by a list of papers and discussions, and of the 
various Committees. We feel sure that this record of work is one that 
has not been surpassed by any other society of similar age and aims and 
that it will carry conviction that the aims which were formulated when 
it commenced work in 1909 are being steadily fulfilled. It is only right, 
therefore, that the Society should now receive the support that it deserves, 
and that the conditions that have hampered its full development should 
now be removed. The Society has been fortunate in obtaining the voluntary 
assistance of many leading men in the profession, and we understand that 
there are several students available to undertake research on various 
aspects of illumination. It is gratifying to observe that the younger 
generation appreciate the necessity of studying the subject, and we look 
forward to their assistance in the near future. 


The Third Report of the Home Office Departmental Committee on Lighting 
in Factories and Workshops. 

The third report recently issued by the Home Office Departmental 
Committee on Lighting in Factories and Workshops marks a new stage 
in the treatment of this subject. The two previous reports have already 
been dealt with in this Journal, but it may be useful to recall some 
of the chief conclusions, now again summarised by the Committee. 

The primary recommendation, contained in the first report (issued 
in 1915) was that there should be a statutory provision requiring adequate 
and suitable lighting in general terms in every part of a factory or work- 
shop, and giving power to the Secretary of State to define adequate and 
suitable lighting. In addition, certain values of illumination (ranging 
from 0*25 to 0'4 foot-candles in working areas) were prescribed in the 
interests of safety and general convenience. In the second report (issued 
1921), general requirements in regard to avoidance of glare, elimination of 
inconvenient shadows and absence of flicker were made. In the report now 
issued the requirements in regard to glare are supplemented by an indica- 
tion that when a brilliant source is covered by a small shade (such as a 
silica cup covering a high-pressure gas mantle or an opal globe surrounding 
a high-power electric source) the brightness may considerably exceed 
15-20 candle-power per square inch and accordingly it should be treated as 
a source, and its position with respect to the worker limited accordingly ; 
on the other hand, this presumably would not apply to such sources as 
ordinary low-pressure mantles properly screened by vitreosil, opal and 
other diffusing materials. 

The chief question left for consideration in this third report was the 
degree of illumination needed for actual carrying on of work, which 
naturally varies according to the industrial process considered. The 
Committee remark that there are two alternative courses of procedure 
(1) Definite minima may be laid down, below which illumination on any 
part of the working plane must not fall ; or (2) Standards of illumination 
may be specified as recommended practice, to serve as guides in determining 
whether lighting is adequate. Such standards would not be legal minima, 
but would conform to the best present practice. 

The Committee has decided, for the present, to adopt the second 
course, and accordingly presents a comprehensive schedule of industrial 
operations divided into two classes, described respectively as " fine work " 
(requiring 3 foot-candles) and " very fine work " (requiring 5 foot-candles). 
Particulars of value specified in the chief American codes are also presented. 

The decision of the Committee is thus in accordance with the judicious 
course indicated at the recent discussion of the Illuminating Engineering 
Society. We think those who study the report must agree that hard 
and fast rules for working illumination would be premature at present, 
and it is much better to defer the fixing of legal minima until, as is sug- 
gested, the subject has been studied in detail with the help of the industries 
concerned. Meantime, we hope that before long effect will be given to 
the Committee's recommendation that there should be a statutory pro- 
vision requiring adequate and suitable lighting in general terms. We are 
glad to note that since the Committee commenced its labours there has 
been a substantial improvement in industrial lighting in this country, 
and there is no doubt that a general requirement of the kind indicated 
would be willingly accepted and would have a beneficial effect. 

B 2 


A Visit to Holland. 

In referring to a visit undertaken by some members of the British 
International Association of Journalists to Roumania last year, we recently 
referred to the interest in illuminating engineering expressed by authorities 
in that country, especially in regard to legislation on industrial lighting.* 
Another opportunity for exchanging views with leading authorities on this 
subject was afforded by the visit of members of the B.I. A. J. to Holland 
during June 2nd-ioth. Holland was among the first of the countries of 
Europe to include in its factory legislation actual values of illumination for 
various industrial processes, and to attach importance to the relation between 
adequate lighting and safety. It was therefore a great pleasure to the writer 
to be granted an interview by the present Secretary of State for Industry, 
Trade and Commerce, Mr. Ysselstein, whom the author first met at the 
International Congress for the Prevention of Industrial Diseases at Brussels 
in 1910. On that occasion Mr. Ysselstein presided when the author's paper 
on Industrial Lighting was read. He was much interested to hear of progress 
in this country, particularly with regard to prospective legislation dealing 
with the lighting of factories and workshops, and fully concurred in the 
principles by which authorities in this country are being guided. In view 
of the anticipation that there may ultimately be international treatment 
of the subject of industrial lighting, such opportunities of exchange of 
views with authorities abroad are of great value. 

The visit proved extremely enjoyable and instructive and there is no 
doubt that there is much in Holland that is of great interest to English 
visitors. In our trips to The Hague, Rotterdam, Amsterdam and other 
cities we were struck by the very orderly and efficient way in which municipal 
arrangements are carried out, and many of the institutions visited were 
object lessons in organisation, cleanliness, and attention to sanitation and 
hygiene. Scheveningen, where the writer and others of the party spent some 
days, is a delightful seaside resort. Holland is rich in historic associations. 
Its central position led to its being the scene of much warfare in the past, 
but it held to its independence with a tenacity which Englishmen must 
needs admire. 

Throughout the tour the party was most hospitably received and enter- 
tained, and it was a special pleasure to meet and exchange views with our 
Dutch journalistic colleagues. The party was also received in the delightful 
rooms of the Legation at The Hague by His Excellency Sir Charles Marling, 
H.M. Minister in Holland. Perhaps the chief impression one received during 
the visit was the close affinity that appears to exist in manners and dis- 
position between the British and the Dutch. They are, as the Dutch 
Minister in London, His Excellency Jonkheer Van Swinderen, happily 
phrased it in his speech at the recent B.I.A.J. Annual Dinner, " chips of 
the same block." 

In conclusion the opportunity may be taken of expressing our apprecia- 
tion of the hospitality of the Official Bureau of Information and Welcome 
to Tourists, presided' over by our esteemed host, Baron F. W. de Tuyll. 
Thanks are also due to the Great Eastern and South Eastern and Chatham 
Railways, the Zeeland Ship Co., and the Dutch Government Railways, for 
granting free passes for the journey, and making special arrangements for 
the comfort of the party. 

Leon Gaster. 

* Illum. Eng.. Mar. 19: 





She illuminating Engineering Society 

(Founded in London, 1909.) 

The Illuminating Engineering Society is not, as a body, responsible 
for the opinions expressed by individual authors or speakers. 


(Proceedings at the Annual Meeting of the Illuminating Engineering Society, held at the House of 
the Royal Society of Arts, 18, John Street, Adelphi, London, W.C., at 8 p.m., on Thursday, 
May 25th, 1922.) 

The Annual Meeting of the Illuminating 
Engineering Society was held at the 
House of the Royal Society of Arts, 
London, at 8 p.m. on Thursday, May 
25th, the Chair being taken by The 
President (Sir John Herbert Parsons, 
C.B.E., F.R.S.). 

The Minutes of the last meeting 
having been taken as read the Hon. 
Secretary read out the names of 
applicants for membership announced 
at the last meeting, who were formally 
declared members of the Society.* 

The Hon. Secretary then proceeded 
to read the usual Report of the Council 
for the Session (pp. 189-193), remarking 
on the varied nature of the topics dis- 
cussed at recent meetings, and the 
exceptional opportunities they had pre- 
sented for joint discussions with kindred 
bodies. The proceedings at the Annual 
Dinner had also served to illustrate 
the many points of contact with the 
medical, architectural and engineering 
professions, and the general recognition 
that now prevailed of the value of the 
Society's work. 

The following resolution was then 
proposed by Mr. T. E. Ritchie, and 

* Illum. Eng., June, 1922, p. 163. 

seconded by Mr. H. A. Carter, both of 
whom referred to the interesting nature 
of recent discussions, and the evidence 
afforded in the report that the Society 
had now completely resumed its pre- 
war activities : — 

" That the Annual Report of the 
Council for the Session, 1921-22, be 
adopted, and that a vote of thanks 
be moved to the Council and Officers 
of the Society for their services during 
the past session." 

The Hon. Secretary then explained 
that there were several vacancies on 
the Council, which, in the absence of 
other nominations, it had been found 
expedient to fill by the nomination 
of Dr. J. F. Crowley, Mr. Phillip 
Sugg and Mr. D. R. Wilson, all of 
whom had kindly consented to act if 

The following resolution was accord- 
ingly put to the meeting by The Chair- 
man, seconded by Mr. L. Gaster, and 
carried unanimously : — 

" That Dr. J. F. Crowley, Mr. 
Phillip Sugg, and Mr. D. R. Wilson 
be elected Members of the Council of 
the Illuminating Engineering Society." 


Ike [■■■■!■! nc«atiiia wm them kit appreciation of tke work that the 

by Tm 'H'JiXA.v. *:_ : Sorietr vm doing in iso— iihajv the 

br' Mr F W Goodococcb, atudy of tke effect of bgkt oa tke 

"TlillkMiMlMi 1cii.«H i ■■ ■■ « *****§•*. «■■■ ' ■* ©pW»l»»« snrgeoa 

• eoro-lToteoftk-tatotkoBorml ^ tfc-e ^^ £7^^ 

Society of Am for tke eaarteoaa m-ck ,,*«£»_ «d ke felt •« 

beem a great phsaai 
to fiatea 

whirh Sir John Hcrh~rt P 
Bocsetr has letesredL 

Hi tanaaaatai 1 •-- fanml tanai — Iks u -f taaafcm, ato*ran exanaaal 

tke ■iilwi^ after which tke Presv h» appreciation, botk of Sir John 1 

r.*.*.. kidna I5»l - '~ am >- ssn earn rmamanl and. of tke rery 

:{rhe*t Panaos», nkle and interesting address which tker 

TVe addreaa emsnaaaaed kad had tke per 

t issiarial nrarataV kasis of tke hoped tkat tke Presides* wot. 

rk. and aptly ssa** nintinn for this to be pnbfiaked 

A problems of inters - 
fiakhnr experts and oasnmdssolse- 
Mfluurj vac given of past work -i-;m;.vt. in briefly acknow- 

->- .- -,-.- : ..".:_** 1 •- ■ ledgmg tke *ate si tinmn "tfi I ■■ 

uaaace besag made to tu appU ** '.-n willingness for tke address to be pabbsked 
tke stady of dsybgkt, an rrUTABT 

.oat swarf rsHfioas added tkat tk*Coaac*l were preparing tke 
jrjnre aa w hvrh mac b researei. 

«od would be glad 

- e of tkaaka to tke Preaideat for to kear from any mem b er s who 
1 address was mo- read papers or 

cat. who. as a payaiofcogist, expre***d ilnsi asa n as. 

Work on Photometry and Illumination. 

' ■ 

r tn- ooatains s spteaai technical sessioa of the 

aaaat by Dr. Earner, Mr. Wai Iflaminataon ' 

irkiey aad Mr Tayi' • liepart mental Committee on 

description ^rtonea and Works), 

e ne» v-grating s p nc rt photo- reseafekes amdertakex ' dnce 

m a sabmar. 

th na inner apher. Baildtasn, aU of wkich 
aster painted white, m ind . 

♦fly as* rnenta have dew 
/aaafled lamps which hlignt est 


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pilotage lights. This is probably the 
first occasion on which the whole subject 
has been thus reviewed. The Chairman, 
in drawing attention to the great impor- 
tance of adequate artificial lighting to the 
future of aerial navigation, invited the 
co-operation of members of the Society in 
dealing with various difficult problems, 
and it is hoped that they will be able to 
render useful service in this connection. 

The next meeting, on February 28th, 
was devoted to a discussion on " Indus- 
trial Lighting ; Ideal Requirements 
(legislative and otherwise) and Practical 
Solutions," opened by Mr. L. Gaster. 
It may be recalled that when the First 
Report of the Departmental Committee 
on Lighting in Factories and Workshops 
was issued in 1915, arrangements were 
made for a full discussion of the report 
before the Society. This discussion 
proved of great value in making the 
Report more widely known and its recom- 
mendations fully understood. Accord- 
ingly the precedent set in 1915 was 
followed at the meeting held on February 
28th, the chief recommendations con- 
tained in the Second Interim Report, 
issued last year, being explained and dis- 
cussed. The opportunity was also taken 
to review developments in other countries, 
particularly the codes of industrial lighting 
adopted in the United States, which in 
principle are in general agreement with 
the recommendations made in this 
country. It is understood that the dis- 
cussion has led to several useful sugges- 
tions, which will be taken into considera- 
tion in giving statutory expression to 
the recommendations made in the 

Following this discussion, an evening 
was appropriately devoted, on March 
28th, to a discussion on " The Lighting 
of Public Buildings ; Scientific Methods 
and Architectural Requirements," ar- 
ranged jointly with the Royal Institute 
of British Architects. At this meeting 
Sir Joseph Petavel, F.R.S., Director of 
the National Physical Laboratory, kindly 
presided, and the introductory paper was 
presented by three members of the staff 
of the Laboratory, Dr. E. H. Rayner, 
Mr. J. W. T. Walsh, and Mr. H. Buckley. 
The paper summarised a comprehensive 
series of tests, undertaken at the request 
of H.M. Office of Works, and carried out in 

the new Ministry of Pensions Building at 
Acton. The thanks of the Society are 
due to H.M. Office of Works for kindly 
granting permission for the publication of 
these comprehensive and useful data. 
Some experiments on the daylight illum- 
ination of a model picture gallery were 
also described, and an account was given 
of the new experimental building being 
erected at the N.P.L. for the purpose of 
facilitating tests of illumination. The 
Council record with pleasure the cordial 
relations existing between the Society 
and the National Physical Laboratory as 
illustrated in this discussion, and it is 
to be hoped that full use will be made of 
the facilities for research at this new 
experimental building. Following the 
reading of the paper, Capt. W. J. Liberty, 
Public Lighting Inspector to the City of 
London, showed a series of photographs 
illustrating methods of lighting adopted 
in various decorative interiors, and a 
number of engineers associated with 
Government Departments and Municipal 
Authorities took part in the discussion. 

This is the first occasion on which a 
joint discussion with the Royal Institute 
of British Architects has been arranged 
by the Society, and it is hoped that there 
will be other opportunities for fruitful 
co-operation with the architectural pro- 
fession in the future. 

The final meeting, on April 25th, prior 
to the Annual Meeting, was occupied by 
the Discussion of " The Use of Light in 
Hospitals," the introductory address, 
delivered by Mr. John Darch, dealing 
specially with the lighting of Hospital 
Wards and Operating Theatres. The 
meeting was arranged jointly with the 
Royal Society of Medicine (Sections of 
Surgery and Ophthalmology), and a 
number of eminent medical men and 
ophthalmic surgeons took part in the 
discussion. A list of queries, inviting 
information on a number of problems, has 
been prepared for circulation, and will, 
it is hoped, prove useful in promoting 
a general understanding of the chief 
principles to be adopted in lighting 

The programme of the Society has thus 
been of a very varied and interesting 
nature, and has afforded an exceptional 
number of opportunities for co-operation 
with other bodies. 



The Annual Dinner. 

The Annual Dinner of the Society was 
held at the Trocadero Restaurant, on 
February 10th, Sir John Herbert Parsons, 
C.B.E., * F.R.S. (President) presiding. 
The Toast of the Illuminating Engineering 
Society was proposed by Sir Herbert 
Jackson (The Royal Society), supported 
by Mr. L. B. Lawford (Chairman of the 
Council of British Ophthalmologists), 
both of whom referred in complimentary 
terms to the work of the Society and the 
opportunities it afforded for co-operation 
between those concerned with various 
aspects of lighting. The toast having 
been responded to by the President, 
Mr. F. W. Goodenough proposed the 
toast of " Kindred Societies," coupled 
with the names of Mr. Thos. Hardie 
(President of the Institution of Gas 
Engineers) and Mr. A. A. Campbell 
Swinton (Vice-President of the Institution 
of Electrical Engineers and Chairman of 
the Royal Society of Arts), both of whom, 
in responding, referred to the value of the 
common platform afforded by the Society 
for friendly discussion on the part of gas 
and electrical engineers. 

The Toast of " The Guests," proposed 
by Mr. L. Gaster, was responded to 
by Mr. R. E. Graves (H.M. Chief Inspector 
of Factories), the Rt. Hon. William Brace 
(Mines Dept.), and Mr. H. E. Blain (Hon. 
Secretary of the British Industrial 
" Safety First " Association). Mr. 
Graves paid a tribute to the pioneering 
work done by the Society in the field of 
industrial lighting, which had paved the 
way for the work of the Home Office 
Departmental Committee on Lighting in 
Factories and Workshops. Mr. Brace 
emphasised the important part played 
by lighting in mines, and recalled the dis- 
cussion which the Society had held on this 
subject in 1920. Mr. Blain referred 
chiefly to the part taken by representa- 
tives of the Society in connection with 
the " Safety First " movement, and the 
growing recognition that adequate illum- 
ination was an essential element in the 
prevention of accidents, both in factories 
and in the streets. 

It was generally agreed that the Dinner 
passed off most successfully and aptly 
illustrated the variety of aspects of 
illumination with which the Society is 
now concerned. 

Among others present may be men- 
tioned : — Major-General Sir Frederick 
Sykes (Controller-General of Civil Avia- 
tion), Mr. J. Herbert Fisher (President of 
the Ophthalmological Society), Mr. 
Joseph Orringe (President of the Electrical 
Contractors Association), Alderman 
George Clark (Chairman of the Society 
of British Gas Industries), Sir William 
Lister, and Mr. W. T. Holmes Spicer. 

Co-operation with other Bodies. 

The arrangement by which the Presi- 
dents of kindred bodies become Members of 
Council of the Society during their tenure 
of office now applies to the following 
bodies whose co-operation continues to 
be of service in dealing with problems of 
mutual interest : — 

The Illuminating Engineering Society 
in the United States ; the Illuminating 
Engineering Society in Japan ; the 
Institution of Gas Engineers ; the Insti- 
tution of Electrical Engineers ; the 
Council of British Ophthalmologists ; the 
Ophthalmological Society ; the Physio- 
logical Society ; the Electrical Contrac- 
tors' Association ; the Society of British 
Gas Industries ; and the Association 
of Railway Electrical and Telegraph 

As mentioned above, the meetings 
during the past session have been par- 
ticularly fruitful in opening up possibilities 
of joint action. As a result of the recent 
discussion on " The Use of Light in 
Hospitals " it is proposed to form a joint 
committee to study this subject in detail, 
and it is hoped that the combined efforts 
of medical men and lighting experts 
will enable some of the main principles 
to be observed in lighting hospitals to 
be more clearly established. 

The new joint committees formed last 
session with a view to studying the 
Lighting of Kinema Studios and the 
question of Glare from Motor Headlights 
have been continuing their work, but at 
present the activities of these and other 
committees are greatly hampered by 
absence of adequate funds for research. 
It is hoped, however, that this difficulty 
will be ultimately overcome. 

Some members of the Illuminating 
Engineering Society accepted the invita- 
tion of the Optical Society to be present 



and take part in a discussion on May 11th 
on Motor Headlights, and an invitation 
was conveyed to the Optical Society to 
nominate a representative to act on the 
Joint Committee formed by the Society. 

Tests on the illumination prevailing on 
typical railway systems are now being 
conducted for the Joint Committee on 
Railway Lighting, and should prove 
useful as a basis for their future conclu- 
sions. The Standing Committee on 
Photometry and Allied Subjects has been 
co-operating with theAdvisory Committee 
on Smoke Abatement attached to the 
Meteorological Office, in regard to the 
absorption of light caused by suspended 
impurities in the atmosphere. The Com- 
mittee has also carried out a considerable 
number of experiments on illumination 
photometers, with a view to ascertaining 
the order of accuracy that can be realised 
in tests in practice. 

The National Illumination Commission 
has now completely resumed its normal 
activities and has drafted a series of units 
and definitions of photometric quantities 
which should serve as a guide to scientific 
procedure in this country. 

Other Events of Interest. 

Various events of great interest, illus- 
trating the growing appreciation of the 
need for the study of illuminating by 
Government Departments, have occurred 
since the termination of the last Session. 
Several of these were mentioned in the 
" Report of Progress during the Vacation" 
presented at the opening meeting in 
November, 1921, and have since been 
fully dealt with in the official organ. It is 
therefore only necessary to recall them 

The issue of the Second Interim Report 
of the Home Office Departmental Com- 
mittee on Lighting in Factories and 
Workshops* last autumn, has been 
dealt with in Mr. Gaster's paper referred 
to above ; and likewise the revised 
version of the Code of the American 
Illuminating Engineering Society which 
contains much of interest to British 
readers. As other instances of reports 
dealing with subjects that have recently 
received attention from the Society may 

* See Illum. Eng., Oct. 1921. 

be mentioned the Third Interim Report 
of the Departmental Committee on Lights 
on Vehicles, and the official report 
issued by the Committee working under 
the Ministry of Health, on the subject of 
the effect of lights in kinema studios on 
vision.* The latter report in many 
respects confirms the views expressed in 
the discussion before the Society in 
January, 1921, and refers with approval 
to the action of the Society in forming a 
Joint Committee to study technical 
problems involved in kinema studio 

It is next of interest to recall that the 
Medical Research Council has appointed 
a Committee to advise them on the pro- 
motion of researches into the biological 
action of light, with a view to obtaining 
better knowledge of the action of sunlight 
and other forms of light upon the human 
body. Professor W. M. Bayliss, one of 
the members of the Council of this Society, 
is Chairman of the Committee. It is 
probable that some of the subjects falling 
within the scope of work of the Committee 
will be of considerable interest to the 
Illuminating Engineering Society. 

An important report has been issued 
by the Committee appointed by the 
Medical Research Council to inquire 
into Miners' Nystagmus. f The Secretary 
of the Committee is Dr. T. L. Llewellyn, 
who read a paper introducing the dis- 
cussion on " The Lighting of Mines, with 
special reference to Miners' Nystagmus " 
in 1920. The report now issued com- 
pletely confirms the conclusion reached 
at the discussion before this Society, 
namely, that the disease is primarily 
due to inadequate illumination. Various 
measures for increasing the available 
illumination, including the use of lamps 
of higher candlepower, or cap-lamps 
which can be brought nearer to the work, 
are recommended. The report consti- 
tutes an important piece of work, and it 
is hoped that the Medical Research Coun- 
cil will take an interest in and support 
the Society's endeavours in other useful 
researches involving the effect of light 
on the eye. 

* See Illum. Eng., Sept, 1921. 

■j- First Report of the Miners' Nystagmus Com- 
mittee (Medical Research Council) : Special 
report series No . 65, Published by H.M. 
Stationery Office. 



International Co-operation in 
Illuminating Engineering. 

A considerable number of papers 
dealing with various aspects of illumina- 
tion have been read before the Illumin- 
ating Engineering Societies in the United 
States, Germany and Japan, and it is 
noteworthy that on several occasions 
subjects have been dealt with by our 
Society which have also been treated in 
discussions before these bodies — thus 
showing that the trend of development 
in the various countries is broadly 
similar. It is hoped that ultimately 
illuminating engineering will receive more 
attention from the nations developing 
in the south-east of Europe, particularly 
Roumania, which was visited by the 
Hon. Secretary of the Society in Septem- 
ber last. In an audience kindly granted 
by the King of Roumania, and in con- 
versations with leading authorities on 
education, the opportunity was taken to 
give some account of the Illuminating 
Engineering movement in this country, 
in which much interest was expressed, 
especially in regard to developments in 
industrial and school lighting. 

The event of outstanding importance 
since the termination of the last session, 
however, has been the First Technical 
Session of the International Illumination 
Commission held in Paris during July 
4th— 8th, 1921. The proceedings have 
already been summarised in the official 
organ. A resolution was passed endorsing 
the adoption of the international candle 
— the unit already in use in this country, 
France and the United States — and a 
tentative series of definitions and units 
for the chief photometric quantities 
has also been framed. This was the first 
occasion on which a series of technical 
papers has been submitted to the Com- 
mission. Discussions took place on a 
number of important subjects, as a result 
of which international technical com- 
mittees dealing with Photometric Defini- 
tions and Symbols, Heterochromatic 
Photometry, Motor Headlights, and Indus- 
trial and School Lighting are being 
formed. It is hoped that this step will 
pave the way for international agreement 
on various outstanding questions, notably 
the question of the ultimate framing of 
international regulations relating to the 

lighting of schools and factories, motor- 
car headlights, etc. 

It will be recalled that in the Report 
for the previous Session, it was mentioned 
that industrial lighting is receiving 
attention from the Section of Industrial 
Hygiene of the International Labour 
Office, established by the League of 
Nations at Geneva. With this work 
Dr. L. Carozzi, a valued corresponding 
member of the Society, is associated. 
The Hon. Secretary has recently had the 
pleasure of meeting Dr. Carozzi, who has 
been on a visit to this country, and dis- 
cussing future methods of co-operation in 
dealing with industrial lighting on an 
international basis. 

Future Prospects of the Society. 

The arrangement whereby two classes 
of members (members and associates) are 
recognised, has operated satisfactorily, 
and has led to a material increase in the 
revenue of the Society, which, however, 
is not sufficient to permit the proper 
expansion of work of which the Society is 
capable. "While the Society can doubtless 
continue on its present lines, it has become 
evident that if it is to extend its operations 
in a manner commensurate with the 
importance of its aims and objects, a 
considerably higher revenue must be 
obtained — either by increase of member- 
ship or in the form of contributions from 
bodies that benefit by the work on which 
the Society is engaged. Another matter 
that is now receiving the attention of the 
Council is the case of members whose sub- 
scriptions are considerably in arrears. 
In many cases this is due to members 
having lost touch with the Society during 
the war period, and it is suggested that in 
such cases some method of compounding 
for the arrears may be adopted. 

The Council are now preparing the 
programme of papers for the next session, 
and invite suggestions from members 
who are prepared to read papers. 

John Herbert Parsons, President. 
Leon Gaster, Hon. Secretary. 





Sir John Herbert Parsons, C.B.E., F.R.S. 

(Delivered at the Annual Meeting of the Illuminating Engineering Society, held at the House of 
the Royal Society of Arts, London, at 8 p.m. on Thursday, May 25th, 1922.) 

The Illuminating Engineering Society, 
from its inception, has concerned itself 
not only with the physical problems of 
devising efficient light sources and appa- 
ratus for its distribution, but also with 
the physiological and pathological effects 
of light upon the human eye. 

For the scientific treatment of the 
physical problems the accurate measure- 
ment of illumination is a fundamental 
necessity. The Society has done much 
to foster investigation in this direction, 
and has been particularly influential in 
the application of measurement to 
domestic and industrial conditions. 
Specially noteworthy is the beneficial 
effect it has exercised on the invention 
and development of simple forms of 
apparatus for measuring illumination. 
These instruments are applicable to both 
natural and artificial light, and whilst 
artificial conditions of lighting have 
presented more numerous and more com- 
plex problems, and have therefore received 
greater attention, natural illumination 
has not been neglected. Daylight illumin- 
ation presents its own specific problems, 
associated with its extreme variability 
due to seasonal and atmospheric changes 
as well as the difficulties associated with 
the topographical orientation of buildings. 
The great variability of sunlight renders 
absolute measurements of illumination at 
any given time of little value, and we owe 
to a former distinguished President of 
this Society, Mr. A. Trotter, the sugges- 
tion of the " daylight factor." The 
practical value of this suggestion has 
been amply proved, largely owing to the 
efforts of one of our members, Mr. 

One of the most important applications 
of the measurement of illumination and 
the " daylight factor " will be found in 
the investigations and recommendations 

of the Factory Lighting Committee of 
the Home Office. Many thousands of 
photometric measurements were made by 
competent observers for this Committee, 
presenting accurate estimates of the 
actual conditions in factories where all 
sorts and conditions of work were being 
carried out. These observations form 
a sure foundation for further investigation 
as to the optimum conditions of illumin- 
ation for various processes and the 
minima permissible from the points of 
view of health and efficiency. Owing to 
the imperative need for national economy 
the Factory Lighting Committee has not 
felt justified on the evidence at present 
available to recommend legal minima for 
industrial processes at the present time. 
In its third interim report, however, it 
has issued schedules of " fine " and " very 
fine " work, specifying standards of 
illumination as " recommended practice " 
for these large and comprehensive groups. 
It cannot be doubted that these guides 
will prove of great value to employers, 
employees, and factory inspectors. Whilst 
avoiding possible hardship attendant 
upon stringent legal minima, they will 
tend to the establishment of optimum 

This Society claims some credit for the 
establishment of the Factory Lighting 
Committee and the work it has done. It 
has not, however, limited its activities 
to factories, but has attacked similar 
problems in connection with schools, 
libraries, shops, streets, railways, etc. 
For example, important reports were 
issued in 1913 by joint Committees on 
School and Library Lighting. In these 
activities the Society has recognised that 
such problems can only be solved by the 
co-operation of lighting experts, those 
who work under the various conditions 
investigated, and those who have made 



a special study of the physiological and 
psychological aspects of vision. 

The fact that an ophthalmic surgeon 
should have been honoured by being 
chosen one of your Presidents, and that 
the Society has several physiologists and 
ophthalmologists among its members and 
serving upon its committees, shows that 
it has always been its policy to give due 
weight to the physiological aspects of the 
problems presented to it. This feature 
is so important that I hope I may be 
forgiven for laying some stress upon it. 

Physicists too often forget that the 
basis of physical measurements is biolo- 
gical, for the so-called " outer world " 
only exists for us by virtue of the sensa- 
tions it arouses in our bodies. Physical 
measurements are open to the errors of 
all human observations, and these vary 
in degree according to the type of 
observation. In all cases the observation 
is the formation of a judgment, based on 
the sensations derived from the stimula- 
tion of a sensory organ. Physiological 
experiments show that stimulation of 
some sensory organs gives more sharply 
defined responses than others. Thus, the 
responses to smell and taste are crude 
and vague ; those to moderate cutaneous 
stimuli — touch and temperature — much 
better defined ; those to auditory stimuli, 
still better, and those to visual best of all. 

But even among the varieties of a 
given type of sensation various degrees 
of definition are met with. Thus pain, 
though cutaneous, is crude like smell 
and taste ; in vision, form sense is much 
more accurately defined than colour 
sense. Definition, indeed, varies as the 
biological differentiation of the sense 

Now, the most highly differentiated 
sensory organ is the eye, and the fovea is 
its most highly differentiated part. Ex- 
periments show that the greatest dis- 
crimination is met with in foveal stimuli. 
The highest degree of sensory discrimin- 
ation is the appreciation of continuity or 
lack of exact continuity in two straight 
lines set end- to end, as in the vernier. 
This may be called linear identity, and it 
is noteworthy that it has been adopted 
empirically by physicists in the vernier, 
balance, and other instruments. Physic- 
ists have been very ingenious in applying 
this criterion to otherwise apparently 

unsuitable measurements, as, for example, 
the measurement of temperature. But 
there are many physical measurements 
to which it cannot be applied, or at any 
rate has not been applied. Photometry is 
an example. Here we are measuring the 
brightness of two lights. By various 
devices the principle of identity or 
equality of sensations is made use of — 
thus utilising the only accurate psycho- 
logical comparison — but the quality of 
the sensation to be adjudicated upon does 
not admit of the accuracy of linear 
identity. Even in homochromatic photo- 
metry we are comparing the brightnesses 
of two illuminated areas. As is well 
known these areas react upon each other 
physiologically — by the process of induc- 
tion or simultaneous contrast. Moreover, 
the judgment is affected by the previous 
stimulation of the retinal areas concerned 
(successive contrast). It is further 
vitiated by variations in adaptation. 

Still more open to error are the com- 
parisons of brightness of different coloured 
lights, heterochromatic photometry. Here 
the difference in colour acts as a very 
disturbing element. Yet by practice it 
is possible to attain almost as accurate 
results as in homochromatic photometry. 
But how can we judge of the accuracy 
of these determinations % In this par- 
ticular instance we can have recourse to 
the fact that the critical frequency of 
flicker depends upon brightness and 
follows a definite mathematical law. The 
eye is extremely sensitive to flicker, so 
that the disappearance of flicker affords 
a very sensitive criterion. It has been 
found that the results obtained by the 
flicker photometer confirm the results 
obtained by the best so-called " equality 
of brightness " observations. 

No matter how delicate the criterion 
there are still errors of observation due 
to imperfections of a biological nature 
common to all human observers and also 
to the so-called " personal equation " of 
the given observer. How are these to 
be eliminated ? Recourse is had to 
mathematical theory. The basis of the 
theory of error, which is a branch of the 
theory of probability, is that small 
errors will be more frequent than large 
ones, very large ones will be practically 
absent, and the mean is the result of the 
mutual destruction or compensation of 



manv small sources of error acting in 
opposite directions. 

The kinetic theory of gases is built 
entirely upon this statistical foundation 
and its success in explaining the physical 
properties of gases is strong evidence in 
favour of the statistical theory. There 
are several mathematical " averages or 
means," and much depends upon the 
choice of the suitable " means/' which 
itself depends upon the frequency dis- 
tribution of the observations. Graphic 
methods of eliminating errors are con- 
stantly used by physicists. One of the 
commonest is the method of interpolation, 
and the smoothing of the curves. 

An interesting example of the opposite 
aspect of averages is the modern view of 
atomic weights. These are some of 
the most accurate physical measurements 
ever made and have been corrected by 
the best statistical methods. Many of 
them approximate nearly to whole 
numbers and there are many theoretical 
reasons for believing that they are 
whole numbers. Recent investigations, 
chiefly by Aston, have shown that the 
atomic weights hitherto obtained are 
themselves averages : that there are 
many so-called " isotopes," having almost 
if not quite identical chemical properties, 
but differing from each other in the 
number of their electrons and also in 
their true atomic weights, which are 
invariably integers. 

I hope that this philosophical paren- 
thesis suffices to show that even in the 
matter of physical measurements the 
physiological aspects of the subject must 
perforce be taken into account. But in 
dealing with illumination we are dealing 
not only with foveal vision, but also 
with peripheral vision and alterations 
of sensitiveness of the eye under different 
conditions of stimulation. It is well 
known that the foveal region of all parts 
of the field of vision alters least in sen- 
sitiveness under different intensities of 
illumination. It is, therefore, relatively 
stable, and observations founded on 
criteria derived from central vision are 
proportionately reliable. It is quite 
otherwise with the other parts of the. 
field of vision. Here the sensitiveness 
of the retina increases enormously with 
diminution of the intensity of stimula- 
tion. This function of retinal adaptation, 

which is of such tremendous practical 
importance in the life of the individual 
and indeed of the species, interferes very 
seriously with the accuracy of scientific 
investigations. Physicists have been led 
astray by ignoring it, as, for example, 
in the so-called " deviations from New- 
ton's law of colour mixtures " described 
bv Konig. Physicists, indeed, are so 
accustomed to dealing with measure- 
ments of the highest order of accuracy, 
founded upon what I have called " linear 
identitv " observations, that they suc- 
cumb to two errors : (1) that of regarding 
these observations as of the supreme 
validity of mathematical abstractions ; 
(2) that of regarding other observations, 
To which the " linear identity " criterion 
is inapplicable, as of far greater accuracy 
than is in fact the case. When the 
mistakes arising from these errors are 
too patent to be ignored, physicists are 
apt to exhibit an unwarranted impatience 
with the shifting sands of biological 
science. The fact must, however, be 
faced that in all cases the observing 
instrument is a living organ and is, 
therefore, in a perpetual state of change. 
The rate of change is relatively slight 
in the most favourable cases, but rapid 
and complex in the less favourable. 
Phvsicists have been notoriously success- 
ful in so reducing the physical complica- 
tions of experiments to a minimum that 
the problem nearly approximates to a 
mathematical abstraction, and, therefore, 
the highest degree of accuracy. Further 
advance is to be sought in greater atten- 
tion to the biological complexities in 
order that they, too. may be subject to 
more complete control. 

A mass of evidence has of recent years 
accumulated to show that in peripheral 
vision two mechanisms are simultaneously 
at work. Of these, one is chiefly con- 
cerned with vision under low intensities 
of light — what I have called scotopic 
vision. The end organ of this mechanism 
is the rods of the retinal neuro-epithelium. 
Photopic vision, or what may be called 
daylight vision, is chiefly carried out by 
the cones. The duplicity theory is so 
well established that it has even found 
its way into the writings of the physicists. 
The explanation and our knowledge of 
retinal adaptation depends upon these 
physiological facts. Since retinal adapta- 



tion plays a preponderant part in simul- 
taneous and successive contrast its import- 
ance in photometry will be readily realised. 

But beyond the field of these well- 
worked problems there exists a vast, 
almost uncharted, area. We talk glibly 
about eye-strain and much has been done 
to alleviate it by correcting errors of 
refraction and muscle balance, determin- 
ing suitable intensities of illumination for 
various types of work, and so on. When 
all this has been done there yet remain 
causes of discomfort and malaise as- 
sociated with the use of the eyes. One 
of the earliest discussions of this Society 
was on Glare. Probably many different 
conditions are included in this omnibus 
term, but we know little more about them 
than we did in 1910. Dirt has been 
described as matter in the wrong place, 
and glare may be fittingly defined as 
light in the wrong place. But when is 
light in the wrong place, and why is it 
wrong ? For practical purposes the three 
forms of glare enumerated in the Factory 
Lighting Report are probably the most 
important : — 

(1) The effect of looking directly at a 
bright sotirce of light, such as an arc 
lamp, so that the observer is for the time 
being prevented from seeing other objects 
properly. He is temporarily dazzled and 
his vision is impaired for a short period 
after the light has ceased to enter his eyes. 

(2) The effect which is produced by 
the presence of one or more bright 
sources of light towards the edge of the 
field of vision so that the rays enter the 
eyes obliquely from them. An observer 
may never look directly at such sources 
of light, but he is nevertheless troubled 
by their presence near to the object at 
which he is looking. This is the com- 
monest form of glare. 

(3) The effect which is produced when 
the surface of cloth, metal, paper or other 
material being worked upon is shiny or 
polished, and reflects light directly from 
some source into the eyes of the worker. 
Many satin cloths, for instance, have a 
" sheen " or a power of regular reflection 
of light which causes work with such 
materials to be very trying unless the 
worker is so placed with reference to the 
source of light that none of the rays can 
be directly affected from the material 
into the eyes. 

These are, however, by no means an 
exhaustive or altogether satisfactory 
treatment of the subject. A certain 
amount of peripheral illumination, for 
example, is beneficial, possibly by causing 
constriction of the pupil. This subject 
alone demands further and prolonged 
research, and it would be easy to enumer- 
ate many other problems which this 
Society is specially adapted to investigate 
in the future. 


The first two reports of the Departmental 
Committee on Lighting in Factories 
and Workshops were issued respectively 
in 1915 and 1921, and have already been 
dealt with in this Journal.* These con- 
clusions are summarised in the third 
report now presented, and it may be 
useful to mention them briefly. 

The most .important recommendation 
made in the first report was that there 
should be statutory provision : — 

(a) Requiring adequate and suitable 
lighting in general terms in every part of 
a factory or workshop ; and 

* Illum. Esq., Sept, 1915 ; Oct. 1921. 

(b) Giving power to the Secretary of 
State to make Orders defining adequate 
and suitable illumination for factories 
and workshops or for any parts thereof 
or for any processes carried on therein. 

In this report minimum values of 
illumination desirable for the sake of 
general safety and convenience were also 
specified. Over the working areas of 
work rooms the minimum horizontal 
illumination specified was 0'25 foot- 
candles and in iron foundries 0'4 foot- 
candles ; 0'25 minimum illumination was 
also recommended in open spaces in 
which persons are employed and on 



dangerous parts of roads, etc. In parts 
of workshops over which persons are 
liable to pass, but actual work is not 
done, a minimum illumination at floor 
level of 01 foot-candles was specified. 
Further recommendations referred to the 
cleaning of windows at reasonable inter- 
vals with the object of securing the 
maximum amount of daylight, etc. 

The second report was devoted chiefly 
to giving recommendations with a view 
to avoiding glare, inconvenient shadows 
on the work, etc. The subject of glare 
was dealt with specially in the following 
clause : — 

(a) Every light source (except one of 
low brightness) within a distance of 100 
feet from any person employed shall be 
so shaded that no part of the filament, 
mantle or flame is distinguishable through 
the shade, unless it be so placed that the 
angle between the line from the eye to 
an unshaded part of a source and a 
horizontal plane is not less than 20°, or 
in the case of any person employed at 
a distance of 6 feet or less from the 
source, not less than 30 in. To this the 
following note is now added : — 

" Examples of sources of low brightness 
are a batswing burner, a paraffin flame, 
etc., and sources of about the same 
brightness as these are not regarded as 
coming within the scope of this recom- 

It should be remembered that the 
covering of a brilliant source by a very 
small shade (such as a silica cup covering 
a high-pressure gas mantle, or a small 
opal globe surrounding a high-power 
electric source) may give this shade or 
globe a brightness more than three or 
four times as great as the five candles 
per square inch, so that it may cause 
considerable glare, in which case it should 
be treated as a source of light in itself. 

The report then proceeds to consider 
the more complicated problem of " work- 
ing illumination," i.e., the illumination 
necessary for the carrying out of industrial 
processes irrespective of the values 
already presented in the interest of 
general convenience and safety. It is 
clearly impossible to specify any one 
standard of illumination of general appli- 
cation. Lighting requirements vary so 

much that every process in each industry 
must be taken into consideration. It 
was, however, thought possible that most 
of the chief processes might be classified 
in a limited number of groups according 
to the illumination needed, and thus the 
whole investigation brought within 
manageable dimensions. 

In dealing with the question of ade- 
quacv two alternative courses of pro- 
cedure present themselves : — 

(1) Definite minima may be laid down, 
below which illumination on any part of 
the working plane must not fall. 

(2) Standards of illumination may be 
specified as recommended practice, to 
serve as guides in determining whether 
lighting is adequate. 

Such standards would not be legal 
minima, but would conform to the best 
present practice, and would represent 
figures which may reasonably fie expected 
for the general standard of illumination 
over the working plane. 

In the course of their inquiry into this 
question the Committee have paid visits 
to a number of factories in which measure- 
ments were made, and have examined the 
codes of industrial lighting adopted in 
the United States of America. The in- 
restigations of the Committee, corro- 
borated by the views of the representa- 
tives of the various industries, led them 
to the conclusion that they could not at 
present recommend the enforcement of 
the legal minima of illumination for 
industrial processes. Requirements must 
be kept low if they are to be enforced as 
legal minima. On a large working plane 
— such, for instance, as a broad loom — 
illumination must vary considerably, and 
points here and there may fall below a 
good standard without much harm, if 
the main area of work is well lit. On the 
other hand, the general standard of 
lighting in progressive factories has risen 
and is rising. It would be unfortunate 
if a too rigid requirement, which must 
be put low, tended to stereotype existing 
conditions, or even to give an excuse for 
depressing general practice. 

The problem is complex. Extensive 
investigations are necessary before it will 
be possible to recommend definite minima 
of illumination to be enforced bv legisla- 



tion. The Committee have, therefore, 
decided to adopt the alternative of 
specified standards of illumination as 
" recommended practice." A schedule 
appended to the report divides the pro- 
cesses in two groups, thus involving 
" fine work " (for which three foot- 
candles is necessary) and " very fine 
work " (for which five foot-candles is 
needed). The schedule is intended to be 
revised from time to time. (See pp. 

Much remains to be done before the 
requirements of factory lighting can be 
established on a basis of definite legal 
minima for illumination. It is suggested 
that if hardship to employers and much 
administrative difficulty is to be avoided, 
any such regulation should be preceded 
by a careful and systematic inquiry 
conducted on two main lines : — 

(i) The collection, for every process 
concerned, of a sufficient number of 
observations to give some indication of 
the best existing practice. 

(ii) Experimental research with the 
object of discovering the conditions of 
illumination desirable on physiological 
and psychological grounds. 

Ample proof is now forthcoming of the 
relationship between lighting on one hand 
and personal safety on the other. It 
therefore seems reasonable to expect 
active co-operation on the part of the 
principal industries in which lighting is 
specially important. The Committee 
accordingly suggests that such industries 
should be invited to assume partial 
responsibility for the scheme specified 
above by arranging for the collection of 
the actual data, possibly through the 
Research Associations where they exist. 

Among other problems studied by the 
Committee special attention has been 
paid to the subject of mixed lighting 
(partly artificial light and partly day- 
light) which appears to be regarded as less 
satisfactory for certain kinds of work 
than either daylight or artificial light 
alone. V\ hile this research does not seem 
to have yet led to any very definite 
conclusions on the main subject of 
inquiry it has clearly indicated the 
desirability of avoiding great contrast 
between the illumination on the working 
area and the brightness of the surround- 

ings. The experience of the workers 
tested, given in an appendix, was that 
" The surrounding darkness acted like a 
nagging foreman, and kept us ' at it,' with 
the result that during the short period 
of the test we increased output far above 
what we could have kept up in that light 
for any length of time/' On the other 
hand the extra effort induced by this 
influence of the lighting led to a feeling 
of great fatigue, and the later substitution 
of semi-indirect lighting was regarded as 
a great relief. 

Another special subject investigated 
by the Committee was the lighting of 
giass-bevelling shops. It appears that 
the difficulty in this case arose from the 
use of unshaded sources within direct 
range of vision of the workers. Such 
local lights should be properly shaded, and 
the Committee also emphasise the de- 
sirability of carrying on the work of glass- 
bevelling wherever possible in workshops 
in which adequate daylight is normally 

Special attention is drawn to the effect 
of lighting on accidents. The Committee 
were particularly impressed by the large 
proportion of fatal falls through ships' 
hatches, due to the inadequate lighting of 
vessels in dock while coaling or under 
repair, and also by several instances in 
factories of accidents due to machinery 
in which a shadow cast upon a danger 
point was a contributory cause. The 
Committee are of opinion that further 
detailed investigation of accidents over 
a longer period, with special reference to 
lighting conditions, is desirable. They feel 
that such an inquiry would be specially 
valuable as regards accidents due to 
" persons falling " which form a large 
proportion of the annual total of accidents 
reported to the Factory Department. 

In addition to the schedule of fine work 
and very fine work referred to above, 
the appendix contains a summary of 
observations of artificial lighting in 
spinning and weaving and other indus- 
tries. Results are illustrated by curves 
showing the degree of illumination met 
with in the various factories visited. 

Another table in the appendix contains 
a summary of values of minimum illumin- 
ation in foot-candles for different processes 
as set out in the American and other 
existing codes. 

20 u 



Processes in the Chief Industries classed as " Fine Work " and 
" Very Fine Work." 

Minimum Standards of Illumination: Recommended Practice. 

SCHEDULE A.— Fine Work. 
3 foot-candles. 

1. All Industries.— Sewing by hand or machines 
of light-coloured material. f 

2. Textile. Weaving on plain, Jacquard, or 
Dobby looms, light-COlOUied materials fine 

counts, dark-coloured materials medium 
or coarse counts and light-coloured materials 
of medium or coarse counts on Jacquard 
looms; Weaving carpets ; Weaving borse- 
hair ; Beaming, winding and warping, 
light-coloured thread fine counts and 
dark-coloured thread of medium or coarse 
counts : Spinning silk ; Spinning gold and 

silver thread; Fustian cutting by hand or 

machine ; Wool sorting and blending. 

Textile, Printing, Bleaching and Dye-work*. — 
Calico printing by hand or machine 
calendering and Bchreenering of cloth. 

Lace.— Slaking lace by hand on pillow ; .Making 
lace, plain nets and curtains by machine: 
Hand scalloping and dipping of machine 
made lace. 

Hosiery (other than making up which set under 
"Sewing"). — Machine knitting (except the 
processes in Schedule B). 

SCHEDULE B.— Very Fine Work. 
5 foot-candles. 

All detailed examination, inspection or gauging 
of articles or parts of articles, whether in 
the warehouse or in any other part of the 
factory or workshop ; Sewing by hand or 
machines of dark-coloured material.f 

Weaving on plain. Jacquard, or Dobby looms 
dark-coloured materials tine counts ; Beam- 
in'_'. winding or warping dark-coloured thread 
line counts; Burling and mending cloth; 
Examining cloth ; Twisting in and drawing-in 
by hand ; Carpet making by hand; Jacquard 
card punching. 

Tambouring of cloth : Engraving metal rollers 
for printing textiles. 

Maki ng lace by hand with a needle ; .Machine 
making of " levers " lace ; Hand darning 
and mending of plain net of " Levers lace ' 
and of 16-point curtain hue ; Pattern card 
cutting or punching. 

Machine knitting processes of linking up and 
running on ; Machine knitting of fine black 
cotton hose ; Hand finishing of gloves and 
hose ; Chevening. 

3. Clothing.^— Sewing light materials (see under 
No. 1) ; Hand pressing or ironing ; Cutting 
out by hand or machine other than band 

Sewing dark materials (see under No. 1) ; 
Button-hole making by hand ; Fur sewing by 
hand ; " Invisible mending " ; Cutting out 
by band knife. 

4. Wigmaking. 

Knotting ; Making net foundations of human 

5. Boots and Shoes. — Closing (stitching uppers) ; 

Beading or embroidering shoes. 

6. Embroidery and Art Needlework.— Em- 
broidery by machine (see under No. 1) 
including embroidering on Swiss em- 
broidery frame. 

All embroidering by hand ; Needle threading 
by hand for Swiss embroidery frame ; Hand 
sewing (fancy stitches) ; Drawn thread 
work ; Tapestry making and repairing. 

* Cmd. 1686 1922. Published by H.M. Stationery Office, Imperial House, Kingsway, W.C. 2. 

f Any kind of sewing (hand or machine) including hemstitching, tucking, braiding, embroidery, 
mending, etc., etc. 

J Any article of clothing and clothing accessories, e.g., Dress making, millinery, tailoring, 
underclothing, hats and caps, gloves, dressing gowns, shirts and collars, neckwear, etc., etc. 



SCHEDULE A.— Fine Work. 
3 foot-candles. 

SCHEDULE B.— Very Fine Work. 
5 foot-candles. 

7. Trimmings. 

Bead trimming ; Sequin sewing by hand and 

8. Artificial flowers. — Mounting flowers. | Making flowers. 

9. Food and Drink. — Pea sorting. 

10. Seed Mixing, etc. (Oil and Seed).— Seed 
sorting and grading. 

11. Tobacco.— Picking. 

12. Glass. — Bevelling; Etching; Sign writing. I Making of cut glass; Polishing lenses and 

prisms ; Smoothing lenses and prisms. 

13. Pottery. — Aerographing (artistic); Transfer Hand painting — fine, 

14. Needles. — "Spitting"; "Battering" and Eye punching and threading. 
" Flattening." 

15. Fish Hooks and Fishing Tackle. — Filing Fly " dressing " or making feathers ; Artificial 
and pointing hooks. bait ; Gut drawing by hand. 

16. Electric Lamps. 

Mounting and bending filaments by hand. 

17. Wood Working. — Cabinet making ; All Wood carving by hand, 
machinery operations, except roughing. 

Furniture and Cabinet making. — Antique fur- — 

niture repairing and restoring ; Inlaying 
and marqueterie. 

18. Upholstery. — Sewing (see under No. 1) ; | Sewing (see under No. 1). 
Carpet planning ; Carpet repairing. J 

19. Brushes. — Dressing, mixing, combing of j Making fine camel's hair brushes, 
bristles, hair, fibre, etc. ; " Drawing " ; , 

Machine planing wooden backs ; Machine 
and hand boring. 

20. Scientific Instruments (Surgical, Dental, 
Optical, Electrical, Mathematical, etc.). 
See also under Engineering No. 29 and 
Class No. 12. — Grinding and finishing. 

Precision working ; Calibration of chemical 
and scientific apparatus. 

21. Clocks and Watches. — Making and Repair- All manual processes. 

22. Jewellery and Precious Stones. 

Bead setting ; Stone setting and mounting ; 
Diamond cutting and polishing ; Enamelling ; 
Pearl stringing ; Pearl fluting and carving ; 
Tortoiseshell inlaying ; Linking and soldering 
gold chains. 

c 2 



SCHEDULE A.— Fine Work: 

3 foot-candles. 

.SCHEDULE B.— Very Fine Work. 
5 foot-candles. 

23. Toys and Games. — (See also under " Engin- 
eering," No. 29 ; " Sewing," No. 1 ; and 
" Wood Working," No. 17.)— Golf Ball 

Musical Instruments. 

Ivory turning and billiard ball turning. 
Drilling and pinning barrels of musical boxes. 

24. Laundry. — Finery ironing. 

25. Cleaning and Job Dyeing. — Examining, i Sewing (see under No. 1). 
mending and pressing of finished articles ; 
Sewing (see under No. 1). 

26. Paper Manufacture. -Examining and sorting | Wall paper designing, 
of suj>erfine sheets. 

27. Printing and Stationery. Stereotyping ; 
Proof-reading; Gold blocking; Relief 
stamping ; Dusting off by hand after 
bronzing ; Almanack. Christmas card, and 
show card finishing and mounting ; Machine 
ruling ; Sign and ticket writing ; Poster 
colouring by hand. 

Box Making. — Making fancy boxes and other 
similar fancy articles; Operating cornet' 
st tying machines. 

Book Binding.- Sewing, chasing, embossing, 
and gilding. 

Composing, including Monotype and Linotype 
machine operating : Drawing by lithographic 
artist ; 8et alto " Engineering," No. 2!>. 

Hand tooling of covers. 

28. Photography. -Photo mounting 

Retouching negatives and prints ; Photo 
colouring ; Painting magic lantern slides. 

29. Metals and Engineering. -Power press 
operations; Pattern making; Soldering 
(where (lone continuously); Armature, 
magneto, and other coil winding: Comb, 
hackle, gill and faller making and setting ; 
Assembling small parts; All accurate 
machine work within the limits of 001 in. 
to 0-001 in. 

Precision grinding ; Tool room operations ; 
Fine metal piercing and stamping; Die 
sinking ; Copper, steel plate and all fine 
metal engraving ; Weaving wire mesh and 
uniting ends of such woven wire ; Very fine 
work, i.e., work done to limits below O'OOl in. 

30. Cutlery. — Hollow grinding and finishing of 
razors ; Burnishing ; Etching ; Cutting 
of bone, ivory, pearl, and wood for scales 
and hafts of cutlery. 

31. File Cutting.— Cutting by hand. 

| Hand cutting of watchmakers' and similar files. 

32. Gold, Silver and Electro Pktte.— Chasing, 

embossing and engraving (medium fine) ; 
Saw piercing ; Cutting out. pressing, 
stamping, spinning, cross-rolling, and tiling 
by hand. 

Chasing, embossing and engraving (fine) 
Burnishing by hand. 


IN ENGLAND (1908-1922). 

The first decade of the twentieth century was marked by a series of advances in 
lamps and lighting appliances. In the field of electric lighting the flame arc, the 
Nernst and tantalum lamps, the mercury vapour lamp, the Moore tube, the tungsten 
vacuum and gas-filled lamps followed in rapid succession. Systems such as petrol 
air-gas lighting were making their influences felt, and substantial improvements in 
gas lighting and acetylene were helping to bring about a revolution in the lighting 
field. All these advances were being recorded in various technical journals, yet there 
was no common centre where all could be discussed and compared. The public 
became bewildered by the rapid march of progress and the variety of choice in 
illuminants available. Illumination had evidently become a more complex question 
than in the past when facilities for lighting were so much more limited. 

People were also becoming conscious that, apart from these advances in lamps, 
there was a need for fuller knowledge as to their proper use ; the circumstances most 
favourable to each type, and the manner in which the light yielded could be best 
distributed and put into service. 

It was this state of things that called the Illuminating Engineering movement 
into existence. Developments were taking place in all parts of the world, and the 
first step was clearly to enlist the support of experts in various countries. As a 
result of visits to the Continent and the United States about 170 authorities on various 
aspects of illumination promised their assistance, and became correspondents of 
The Illuminating Engineer, formed in 1908, which was the first English Journal 
to deal exclusively with lighting by all illuminants, and to act as a centre of information 
on this subject. 

After the Journal had been in existence a year, and had been instrumental in 
making the idea of " illuminating engineering " (the term adopted to cover all matters 
connected with the application of light in the service of mankind) more familiar, 
it became apparent that there existed a nucleus of people anxious to exchange views 
and promote a better understanding of the benefits of good illumination. Accordingly 
the Illuminating Engineering Society was formed in 1909, under the Presidency of 
the late Professor Silvanus P. Thompson, whose inaugural address contained an 
admirable summary of its aims and objects. Experts in the chief cities throughout 
the world were made corresponding members and the Society enjoyed the benefit 
of their experience in many ensuing discussions. 

Hitherto the choice of systems of lighting had usually been regarded merely as 
a matter of cost, with the result that people grudged the necessary expenditure to 
secure adequate illumination, and did not discriminate between crude inefficient 
devices and those designed on scientific principles. It was not yet sufficiently 
realised that inadequate illumination is dear at any price, and that each application 
of light — whether in the home, in streets, schools, libraries, factories, etc. — presents 
special problems and requires careful study. There was, in fact, little information 
as to the best methods of nsing light, and the benefits of good illumination were not 
sufficiently appreciated. 

The Illuminating Engineering Society accordingly set itself the task of pro- 
viding a centre for the collection of information on all aspects of illumination and 
providing a platform on which representatives of different systems of lighting could 
meet for friendly discussion. From the outset it was apparent that there are many 
problems of common interest for them to consider, and that they were united in 
their desire to educate the public to a better recognition of the importance of good 


The Society has now been in existence for more than twelve years and the 
common platform it provides for discussing these various problems has been much 
appreciated by gas and electrical engineers. Its membership now approaches 500 
and includes not only lighting experts, but architects, medical men, inspectors of 
factories, railway engineers and others concerned with illumination. 

Kecognising that " Light is the Cause, Illumination the Effect," and that with 
this effect all sections of the community are concerned, the Society has been instru- 
mental in bringing together the supplier of gas and electricity, the makers of lamps 
and lighting appliances, and the actual users of light. All classes have been repre- 
sented in its varied discussions, a feature of which has been the numerous joint 
meetings with other bodies concerned with the particular application of light under 
consideration. In this way the circle of those interested in the Society's work has 
been continually extended. Many different sections of the public have been shown 
that the maintenance of good illumination is of direct interest to them in their daily 
work. On various occasions Government Departments have also taken an active 
interest in the discussions of the Society. 

As a result of these discussions much has been learned on the subject of 
illumination. The fundamental principles of good lighting are now becoming clearly 
established and the position is utterly different from what it was twelve years ago, 
when the Society commenced its work. The opportunities for discussion of all 
aspects of lighting have, led to great technical advances. There has been great 
progress not only in the lamps available, but in the fittings whereby their light is 
usefully distributed and used to the best advantage. Simple and convenient in- 
struments have been devised, enabling records of illumination to be obtained in 
buildings of all kinds, so that we now understand much better how to determine 
and supply the illumination required for any process, to increase the illumination 
where needed and to check waste where it exists. Another important step has been 
the increased interest taken in illumination by the medical profession and especially 
by ophthalmologists, amongst whom the services of the present President of the 
Society, Sir John Herbert Parsons, C.B.E., F.R.S., deserve special mention. It 
is now recognised that the physical problem of producing light as efficiently as possible 
is only part of the question, that it is equally important to consider the effect of this 
light on the eye, by which we are ultimately guided in judging the effect of an 

Apart from the publicity given to the aims and objects of the Society through 
its discussions, and their reproduction in The Illuminating Engineer, the official 
organ of the Society, great assistance has been obtained from the daily and technical 
press. References to the work of the Society habitually appear in more than 100 
publications. On the technical side a feature has been the formation of numerous 
joint committees, by whom subjects suggested by discussions are considered in fuller 
detail, and reports issued. 

In the following pages a more detailed account of the Society's work is presented. 
The list of papers and discussions (pp. 209-214) shows that, considering its present 
resources, the Society is amply fulfilling the objects for which it was created. Its 
influence has been beneficial alike to the public and the lighting industry. The 
former have been shown how to use their light to better advantage. The latter 
have found their efforts simplified by the growing demand for better lighting, and 
the appreciation of the benefits of scientific methods in applying light in the service 
of mankind. The time is now ripe for the extension of these activities on a 
larger scale. 

THE lLU'MIXATIXc HNOINEEB (july L922) 205 




The Illuminating Engineering Society has provided a platform for the impartial 
discussion Of illumination, a friendly meeting place for architects, medical men and 
engineers connected with all methods of lighting. It is most important to the lighting 
industry that this atmosphere of " fair play " should be maintained. 

During its 12 years of existence the Society has held 84 meetings. The total 
attendance, obtained by adding up the number of people present at each meeting, 
approaches, 5,000, approximately 60 per cent, of whom were visitors specially interested 
in the various subjects discussed. Upwards of 800 contributions have been made 
to the discussions. 

The proceedings have been regularly reported in the official organ, The 
Illuminating Engineer, and have received a unique and widespread attention 
in the technical and daily press. The Journal is habitually quoted by over 100 
periodicals and daily papers, and the movement is thus brought to the notice of millions 
of people every year. 

By the efforts of the Society, articles dealing with various aspects of illumination 
have also appeared in many special journals read in circles which it was desired to 
influence in favour of good illumination. 

Besides appealing to the general public, the movement receives support from 
many distinguished engineers and scientific men. Its first President was the late 
Professor Silvanus P. Thompson, D.Sc, F.R.S., whose successors in office were Sir 
William Bennett, K.C.V.O., F.R.C.S., Surgeon to H.M. the King, and Mr. A. P. Trotter, 
who has been responsible for much early pioneering work in photometry and illumina- 
tion. The President for the current year is Sir John Herbert Parsons, C.B.E., F.R.S., 
one of the most eminent ophthalmologists in this country, who has taken a great 
interest in the study of the effects of light upon the eye, and the application of know- 
ledge of this subject in illuminating engineering. 

The movement enlists the sympathy of those associated with pure and applied 
science engineering and architecture. At the Annual Dinners of the Society, for 
example, the Society has been honoured by the presence of, among others, the follow- 
ing distinguished guests : — The Presidents of the Royal Society, the Institutions of 
Gas and Electrical Engineers, and the Ophthalmological Society, the Chairman of the 
Council of British Ophthalmologists, the Controller-General of Civil Aviation (Air 
Ministry), H.M. Chief Inspector of Factories, the Director of the Mines Department, 
the Director of the National Physical Laboratory, the Secretary of the Department for 
Scientific and Industrial Research, the Chairman of the Royal Society of Arts, the 
President of the Institution of County and Municipal Engineers, the Chairman of the 
Society of British Gas Industries, the President of the Electrical Contractors' Associa- 
tion ; whilst among other bodies and Government Departments represented may be 
mentioned the Ministry of Munitions, the British Science Guild, the Royal Institute 
of British Architects, the London " Safety First " Council, etc 

With many of these bodies the Society maintains intimate relations, and in 
order to facilitate co-operation on subjects of mutual interest, an arrangement has 
been made by which the acting Presidents in many cases become members of Council 
of the Illuminating Engineering Society (see page 208). The Society has also been 
added to the list of constituent bodies of the Conjoint Board of Scientific Societies. 

On the occasion of the Tenth Anniversary of the official organ of the Society 
(The Illuminating Engineer) a series of messages from sixty prominent scientific 
men, representatives of the leading firms associated with the manufacture of lamps 


and lighting appliances and companies engaged in the supply of gas and electricity, 
besides experts interested in the hygienic and other special aspects of illumination 
were received, all expressing keen sympathy and interest in the aims and objects of 
the Society.* This illustrates the wide circle to whom the movement for better 
illumination appeals. 

The Society interests all classes. It brings the manufacturer of lighting ap- 
pliances in contact with the actual user of them. For example, when discussing 
Library Lighting a Joint Meeting with the Library Association was arranged ; sub- 
sequently the proceedings were reprinted by the Library Association and distributed 
among all its members. Similarly, when dealing with School Lighting, the co-operation 
of medical and educational authorities was secured. Subsequently Joint Committees 
on School and Library Lighting were formed. These Committees have already issued 
interim reports on these subjects, f which have received attention in most influential 
quarters. Already, through the work of our Society, the standard of lighting in many 
schools through the country is being raised. 

The Illuminating Engineering Society was also instrumental in forming the 
Joint Committee on the Standard Specification for Street Lighting, on which, for the 
first time, delegates from the Institutions of Gas, Electrical, and Municipal and 
County Engineers worked together. Wishing to provide an opportunity for open 
discussion of this difficult subject the Committee determined to avail themselves of 
the impartial platform of the Illuminating Engineering Society. The paper read by 
Mr. A. P, Trotter on the subject attracted notice far and wide throughout the country 
and has already done much to raise the status of street lighting. J 

Since the illuminating engineering movement was started a continually increasing 
amount of attention has been paid to illumination in the reports of H.M. Chief 
Inspector of Factories. This has culminated in the appointment by the Home 
Secretary of a Departmental Committee to inquire into Industrial Illumination, which 
issued a most valuable and comprehensive interim report in 1915,$ recommending 
that there should be statutory provision requiring : " (a) Adequate and suitable 
lighting in general terms in every part of a factory or workshop, and (b) giving power 
to the Secretary of State to make Orders defining adequate and suitable illumination 
for factories or workshops or for any parts thereof or for any processes carried on 
therein." Supplementary reports, containing recommendations on the avoidance 
of glare, inconvenient shadows, etc., and classifying industrial processes according 
to the illumination considered desirable in practice have also been issued in 1921 1| 
and in the present year. Meantime in seven of the United States (New York, New 
Jersey, Pennsylvania, Ohio, Wisconsin, California and Oregon) codes of industrial 
lighting are in actual operation, and it is anticipated that the matter will be the 
subject of international consideration in the near future. In addition the subject of 
industrial lighting is receiving attention from the Department of Industrial Hygiene 
of the League of Nations at Geneva, with which Dr. Carozzi, a valued corresponding 
member of the Society, is associated. 

An important element in the Society's work has been its encouragement of good 
illumination in the interests of safety which is aided by the representation of the 
Society on the London " Safety First " Council, and on the kindred body established 
to deal with industry, the British Industrial " Safety First " Association. A 
pamphlet emphasising the value of good lighting in the interests of safety has been 
issued and widely circulated by this body. 

Another subject wh^re the facilities for co-operation already established with 
the Council of British Ophthalmologists and other bodies concerned with the study 
of vision will be valuable is the Effect of Light on the Eye. The Society was re- 
presented on the committee formed under the auspices of the above-named Council to 
study the illumination of optical test-charts. It has also received most valuable 

* Illum; Eng., Jan., 1918. J Illum. Eng., May and June. 1913; 

f Illum. Eng., July,- 1913; and July* 1914; § Illum. Eng., Sept., 1915. 

jl Illum. Eno ; . Oct.. 1921; 


assistance from this body in connection with the Joint Committee appointed at the 
request of the London County Council to inquire into the question of Eyestrain in 
Cinemas, which reported in 1920.* 

During the war, the Society, at the request of the Ministry of Munitions, formed 
two committees to undertake researches on radioactive self-luminous materials having 
special war applications, and on the illuminating power of flares, parachute lights, 
etc.f Both committees conducted exhaustive experiments and issued reports which 
were much appreciated, and received the cordial thanks of the Ministry for their 
services. In connection with Economy in Lighting a series of recommendations to 
consumers was issued (with the concurrence of the Board of Trade) showing how 
the requirements of the Household Fuel and Lighting Order could be most readily 
complied with.J The Society and its members have also assisted by advice and 
experiment on many other technical matters during the war, and discussions at 
meetings on such subjects as Searchlights, the Lighting of Rifle Ranges, etc., have 
proved most helpful. 

With the termination of hostilities and the resumption of more normal con- 
ditions, the Society has quickly established new connections. A feature of recent 
activities has been the large number of occasions on which joint discussions with 
other bodies have been arranged. As instances may be mentioned the recent meetings 
devoted to The Use of Light in Aerial Navigation, when a joint discussion with the 
Royal Aeronautical Society was arranged ; the discussion on The Lighting of Public 
Buildings, when the co-operation of the Royal Institute of British Architects was 
invited ; and the joint meeting with the Royal Society of Medicine (Sections of 
Surgery and Ophthalmology) devoted to the subject of The Use of Light in Hospitals. 

A number of new committees, including those appointed to deal with Railway 
Lighting, The Lighting of Kinema Studios and Motor-Headlights have been formed, 
and another on Hospital Lighting is contemplated. 

It will be seen that the Society is continually extending its field of activities 
and reaching new sections of the public. It is hoped in the future to arrange for 
local centres in the provinces, where subjects of special interest to these localities 
can be discussed. 

From the commencement of the Society's work it has aimed at an international 
connection in order that members may be kept abreast of progress in illumination in 
various parts of the world. Prior to the war, the Society was frequently represented 
at international congresses, amongst which may be mentioned : — ■ 

The International Congress on Industrial Hygiene (Brussels. 1910). 

The International Hygiene Congress (Dresden, 1911). 

The International Electrical Congress (Turin, 1911). 

The First International Congress for the Prevention of Industrial Accidents (Milan, 1912). 

The Fourth International Congress of School Hygiene (Buffalo, 1913). 

The Annual Congress of the Royal Institute of Public Health (Paris, 1913 ; Brussels, 1920). 

The First Technical Session of the International Illumination Commission (Paris, 1921). 

During the war such activities were naturally interrupted. But opportunities 
of attending congresses where useful work can be done, now present themselves once 
more. The Society was represented at the Congress of the Royal Institute of Public 
Health, held in Paris in May, 1920, when industrial lighting and other topics of 
interest to illuminating engineers were discussed. A most important event was the 
holding of the First Technical Session of the International Illumination Commission 
held in Paris during July 4th-8th, 1921, when a series of papers on various aspects 
of illumination and photometry was presented, and' important resolutions passed. 

There have also been opportunities of visiting Belgium, Holland, Roumania 
and Czecho-Slovakia, and interesting authorities in illuminating engineering. In 
this way an interest in the subject may be kindled in many parts of the world, so that 
ultimately the subject will be treated on an international basis. 

* Illu.m. Eng., June, 1920. t IuuiM. Eng., May and July, 1918. 

t Illx'm. Eng., Nov. and Dec. 1018. § Illum; Eng.; Sept.. Oct., 1921. 




Gbe Slluminating Engineering Society. 

(Founded in London, 1909.) 
President — Sir John Herbert Parsons, C.B.E., F.R.S., 54, Queen Anne Street, W.l. 
Members of Council — 
A. Blok, B.Sc., A.M.I.E.E., Lecturer in Electrical Engineering, Croydon Polytechnic, 

45, Plympton Road, Brondesbury. 
F. Bailey, Chief Engineer to the City of London Electric Lighting Co., Ltd., 64, 

Bankside, S.E. 
Prof. Sir Wm. M. Bayliss, M.A., D.Sc, F.R.S., Assistant Professor of Physiology 

at University College, London, St. Cuthbert's, Hampstead Heath, London. 
Prof. W.C.Clintov. Assistant Professor of Electrical Engineering, University College, 

43, Stanhope Gardens, Highgate, London, N.6. 
S. H. Callow, English Electric and Siemens Supplies. Ltd., 38-39, Upper Thames 

Street, E.C.4. 
Dr. J. F. Crowley, B.A., Consulting Engineer, Lamb Buildings, Temple, E.C. 
J. Darch, F.S.E, .Mem. Roy. San. [nst., •"."». West Side. Wandsworth Common, London, 

J. S. Dow, Asst. Editor of The Illtmix atixo Engineer, Mavtield, Shepherds Hill, 

Highgate, London, N.fl. 
J. E. Edgecombe, Director of the Electric Lamp Manufacturers' Association of 

Great Britain, Ltd., Ehna House, 2.1, Bedford Square, London, W.C.I. 
J. Eck, M.I.E.E., 10, Priory Road, Chiswiok, W. 
L. Gaster, Consulting Engineer ami Editor of The Illuminating Engineer, etc, 

32, Victoria Street, S.W.I. 
F. W. Goodenough, Mem. Lust. Gas Engineers, Sales Controller of the Gas Light 

and Coke Co., Horseferrv Road, Loin Ion, S.W. 
Haydn T. Harrison, M.I,E.E., Electrical Engineer, 11, Victoria Street, S.W.I. 
J. Wyatt Ife, Lighting Engineer, Holophane, Ltd., Vincent Square, Elverton Street, 

London, S.W.I. 
Dr. James Kerr, Medical Officer, London County Council Education Offices, Public 

Health Dept., Room 2::. 2, Savoy Hill, Victoria Embankment, W.C. 
F. A. Cortez Leigh, Chief Electrical Engineer, London and North Western Railway, 

Euston Station, N.W. 
Dr. R. Lessing, Ph.D., F.C.S., Consulting and Analytical Chemist, Southampton 

House, 317, High Holborn, W.C. 
Dr. A. H. Levy, M.D., F.R.C.S., Ophthalmic Surgeon, Central London Ophthalmic 

Hospital, 67, Wimpole Street, Cavendish Square, W.C. 
Ca;pt. W. J. Liberty, Public Lighting [nspector to the City of London, 55, Beckwith 

Road, Heme Hill, London, S.E. 
W. R. Rawlincs, Electrical Contracting Engineer, Past President of the Electrical 

Contractors' Association, 82, Gloucester Road, South Kensington, S.W. 
P. Sugg, Director of Wm. Sugg & Co., Chapter Street, Westminster, S.W.I. 
A. Stokes, Chief Outdoor Inspector of the South Metropolitan Gas Co., 709, Old 

Kent Road, London, S.E. 
S. E. Thornton, Consulting Engineer, 17, Victoria Street, London, S.W.I. 
P. J. Waldram, F.S.I., Surveyor and Civil Engineer, " Robinscroft," Second Avenue, 

D. R. Wilson, H.M. Inspector of Factories, 7, Sydney Place, S.W. 7. 
Hon. Secretary — L. Gaster. Hon. Assistant Secretary — J. S. Dow. Hon. Treasurer — 

J. Wyatt Ife. 

Hon. Solicitors — Messrs. G. M. Light & Fulton, 1, Laurence Pountney Hill, Cannon 
Street, E.C. 

In addition, the Acting Presidents of the following bodies become members of the 
Council of the Illuminating Engineering Society during their term of office : — 

The Illuminating Engineering Society in the United States ; The Illuminating Engineering 
Society in Japan; The Institution of Gas Engineers; The Institution of Electrical Engineers ; 
The Council of British Ophthahnolojists ; The Ophthalmological Society; The Physiological 
Society; The Electrical Contractors' Association ; The Society of British Gas Industries; and 
The Association of Railway and Telegraph Engineers. 



ZTbc illuminating lEncjmccrino Society 

(Founded in London), 


Nov. 18 Inaugural Address. By Prof. Silvanus P. Thompson. 

Jan. 11 Glare, Its Causes and Effects. By J. Herbert Parsons. 

Feb. 15 Discussed by : — 

Great Britain— Dr. F. W. Edridge Green, Dr. F. Gans, Dr. J. Kerr, Dr. W. Ettles, 
Dr. T. M. Legge, Dr. W. M. Bayliss, P. J. Waldram, A. P. Trotter, J. H. 
Agar Baugh, J. S. Dow, W. R. Cooper, W. M. Mordey, Haydn T. Harrison, 
V. H. Mackinney, L. Gaster, Dr. S. P. Thompson, Dr. E. H. Nash, Dr. W. Ettles, 
Prof. G. J. Burch. 

Abroad— Dr. K. Stockhausen (Dresden), Prof. L. Weber (Kiel), Dr. Corsepius 
(Cologne), Dr. L. Bell (Boston), Dr. E. P. Hyde (Cleveland), Prof. R. Ulbricht 
(Dresden), Dr. L. Bloch (Berlin), M. Lauriol (Paris), Prof. S. A. Rumi (Genoa), 
Dr. W. H. Seabrook (New York), Dr. E. 0. Sisson (Denver), Dr. W. Voege 
(Hamburg), Dr. H. Kriiss (Hamburg), Prof. H. Strache (Vienna), H. Prenger 
(Cologne), Dr. H. Lux (Berlin), Prof. A. Grau (Vienna), Messrs. Korting and 
Mathiesen (Berlin), C. H. Williams (Boston) (19). 

Mar. 15 The Measurement of Light and Illumination (General Discussion). 

April 14 Discussed by : — 

Great Britain— Prof. A. E. Vernon Harcourt, Dr. J. A. Fleming, A. P. Trotter, 
C. C. Paterson, Dr. W. E. Sumpner, W. J. Liberty, Prof. J. T. Morris, J. S. Dow, 
L. Wild, J. G. Clark, Haydn T. Harrison, P. J. Waldram, K. Edgcumbe, L. 
Gaster, W. R. Cooper, G. F. Boxall (16). 
Abroad— Br. K. Stockhausen (Dresden), Dr. L. Bell (Boston), Dr. C. H. Sharp 
(New York), G. H. Stickney (Schenectady), F. Lauriol (Paris), Prof. A. Blondel 
(Paris), Dr. Corsepius (Cologne), W. J. Cady (New York), A. A. Wohlauer (New 
York), N. Macbeth (New Jersey) (10). 
April 14 The Direct Measurement of the Total Light Emitted from a Lamp. 

By Dr. W. E. Sumpner. (6) 
Nov. 8 Recent Progress in and the Present Status of Gaslighting. By 


Dec. 9 Recent Progress in Electric Lighting. By Dr. W. E. Marchant. 

Note on the Blackening of Tungsten Lamps. By G. W. Howe. (16) 


The Artificial Lighting of Libraries. By J. Duff Brown, L. S. 
Jast, J. Darch. (25) 

(Joint Meeting with the Library Association.) 
The Natural Lighting of Schools. By Dr. J. Kerr. 
The Artificial Lighting of Schools. By Dr. N. Bishop Harm an. (25) 
Joint Meeting with the Association of Medical Officers in Schools, the 
London Teachers' Association, and the Association of Technical 
April 24 Interior Illumination and the Reflecting Power of Walls and 

Ceilings. By Haydn T. Harrison and P. J. Waldram. (12) 
Nov. 17 Notes on the Design of Motor-Car Headlights. By Dr. H. R. B. 

Hickman. (10) 
Dec. 19 Lighting of Railway Stations and Goods Yards. By Haydn T. 
Harrison. (15) 

[The numbers in parentheses at the end of each reference indicates the number of persons 
tit king part in the discnssion.~\ 









List of Papers read before the Illuminating Kngim-.-niig Society — (continued): — 


Jan. 16 Colour Discrimination by Artificial Light. By T. E. Ritchie. (15) 
Feb. 20 Shop Lighting by Electricity. By N. W. Prangnell. 

Shop Lighting by Gas. By A. E. Broadberry. (16) 
Mar. 19 Illumination of Printing Works by Electricity. By J. Eck. 

Illumination of Printing Works by Gas. By F. W. Goodenough. (11) 
April 15 Private House Lighting by Electricity. By W. R. Ra\ylin<;s. 

Private House Lighting by Gas. By W. BE. Y. Webber. (12) 
Nov. 19 Recent Progress in Illuminating Engineering. By L. Gaster. 

A New Illumination Photometer. By Haydn T. Harrison. 

Photography in Illcmin attng Engineering. By J. S. Dow. 

Apparatus to Illustrate Reflections from Walls and the Ceiling. 
By Prof. W. ('. Clinton. (12) 
Dee. 3 Modern Methods of Indirect Lighting. By F. W. Wn.i.cox and 
H. C. Wheat. (14) 


Jan. 14 Acetylene Lighting. By C. Hoddle. 

Petrol-Air Gas Lighting. By E. Scott Snell, (15) 
Feb. 18 Some Notes <>n the Use of Shades \m> Reflectors. By .1. G. Clare 

and V. H. Mackinney. (14) 
Mar. 11 The Centenary of <i\s Lighting \m> its Historical Development. 

By W. .1. Liberty. (5) 
April 15 Standard CLAUSES for Insertion in a SPECIFICATION OF Street - 

& lighting. By A. P. Trotter. 

April 29 Discussed by: — 

Great Britain W. II. Patchell, F. W. Goodenough, Haydn T. Harrison. P,. Watson, 
.1. G. ('lark. F. Thorp, K. Edgcumbe, J. Darch, EL T. Wilkinson. Prof. J. T. 
Morris, .1. \V. Bradley, F. Bailey, F. Allen. Roger T. Smith. \V. 1!. Cooper, 
J., L. Gaster, N. \V. Prangnell, S. L Pearce, H. A. Ratcliff, J. G. Clark, 
.1. S. Dow, W. .1. Liberty (23). 

Abroad — Dr. L. Blooh (Berlin), Dr. L J. Terneden (Amsterdam), Prof. H. Stracho 
(Vienna), Prof. X. A. Rumi (Genoa), Dr. I,, licll (Boston). L B. Marks (New 
Fork), l>r. C. IF Sharp (New York), P. 8. Millar (New York) (8). 

Nov. 18 Retort of Progress during Vacation. By L. Gaster. 

Illumination at the National Gas Exhibition. By F. W. < Ioodenough. 
Some Notes on the Fourth International Congress of School 

Hygiene. By Dr. James Kerr. 
Shadows by Natural and Artificial Light. By .T. S. Dow and V. H. 

Mackinney. (5) 
The Importance of Direction. Quality and Distribution of Light. 
By M. Luckiksh. 
Dec. 16 Some Problems in Daylight Illumination. By P. J. Waldram. 

Jan. 15 Discussion of above paper : — 

Great Britain— G. Widdows, Dr. J. Kerr, J. S. Dow. F. R. Farrow. Dr. E. H. 
Nash, A. P. Trotter, W. C. Clinton, H. L. Dunstall, C. C. Paterson, P. L. Mark.-, 
W. H. Webb, Dr. F. (Jans. J. S. Dow. V. H. Mackinnev. L. Gaster, T. E. Ritchie, 
L. Wanen. P. J. Waldram (18). 

Abroad — Prof. L. Weber (Kiel), Dr. F. Pleier (Karlsbad), Dr. L. Burgerstein 
(Vienna), Dr. F. Altschul (Prag), Dr. Erisman (Zurich), Dr. Kaz (St. Petersburg). 
Prof. Richtmeyer (Ithaca, U.S.A.), Dr. Max Graber (Munich) (8). 

Feb. 17 The Lighting of Picture Galleries and Art Studios. By Prof. 

Silvanus P. Thompson. (15) 
Mar. 17 A Comparison of Estimated and Observed Values of Illumination 

in Some Lighting Installations. By W. C. ClInton. (13) 
April 7 The Lighting of Railway Carriages and other Public Vehicles 

(Discussion). (9) 


List of Papers read before the Illuminating Engineering Society — {continued) : — 

May 21 The Nomenclature and Definition of Photometric Magnitudes and 
Units. By A. P. Trotter. 
Discussed by : — 

Great Britain — Dr. S. P. Thompson, C. C. Paterson, Havdn T. Harrison. F. W. 
Goodenough, \Y. ('. Clinton. E. Allen, K. Edgcumbe/j. T. Morris. W. J. A. 
Buttcrfield, J. Darch, W. J. Liberty. V. H. Mackinnev. A. V. Belltell, Dr. A. 
Schuster, J. S. Dow. W. R. Cooper, J. W. T. Walsh (17). 

Abroad— Dr. L. Bell (Boston). Prof. A. Blondcl (Paris), Prof. Dr. H. Bunte (Karls- 
ruhe) (3). 

Dec. 1 Illuminating Engineering in War Time. By L. Gaster. (10) 

Jan. 19 Searchlights, their Scientific Development and Practical Appli- 
cation. By P. G. Ledger. (15) 
Feb. 16 The Development and Design of Lighting Fixtures in relation to 
Architecture, Interior Decoration and Illumination. By F. W. 
Thorpe. (17) 
Mar. 16 The Rating and Grading of Lamps and the Best Methods of Speci- 
fying their Illuminating Value. By F. W. Willcox. (20) 
April 27 Visibility : Its Practical Aspects. By C. C. Paterson and B. P. 

Dudding. (11) 
May 18 Some Points in Connection with the Lighting of Rifle Ranges. 
By A. P. Trotter. 
Discussed by : — 

A. Blok, A. Schamasch. P. J. Waldram, H. Brazil. Col. Gaitskell Burr. H. Fieak, 
W. J. Bassett, G. Herbert, the Commandant of the Royal School of Musketry, 
Hythe, F. Bailey. S. G. Coram, T. B. Pickard. J. G. Clark. W. Ettles, the Com- 
mandant of Royal Marines Depot, Deal, J. S. Dow, Frank West (Hon. Secretary 
of Rifle Club at the India Office) (17). 
Nov. 23 Notes on the First Report of the Departmental Home Office 
Committee on Lighting in Factories and Workshops. By L. 
G aster. (12) 
Dec. 10 Recent Developments in Electric Incandescent Lamps in Relation 
to Illuminating Engineering. By Prof. J. T. McGregor Morris. 



Jan. 11 Some Principles in Industrial Lighting. By J. S. Dow. (12) 

Feb. 22 Some Future Possibilities in the Design of Instruments for Measur- 
ing Illumination. (17) 

Mar. 31 Some Aspects of the Design and L x se of Glassware in Relation to 
Natural and Artificial Illumination. By S. B. Langlands. (21) 

May 9 Interim Report of the Committee on Research. 

Dec. 15 Some Events during the Vacation with Special Reference to War 
Economies in Lighting. By L. Gaster. (7) 

Jan. 16 The Lumen as a Measure of Illuminating Power. By Prof. J. T. 

McGregor Morris, F. W. Willcox. (15) 
Feb. 20 The Effect on the Eye of Various Degrees of Brightness and 
Contrast. By Dr. James Kerr. 

(The Cinema Commissio)i^ of Inquiry uas represented at this 
Discussed by : — 

Sir William Bennett, Dr. Ernest Clarke. M.I'.. F.R.C.S., N. Bishop Harman, 

Colin X. Bennett, E. G. Kennar'l. p> r . ('. \y. Kimmins (Member of the Cinema 

Commission of Inquiry) ; L.C.C. Chief Inspector of Schools, A. E. Xewbould 

(Member of the Cinema Commission of Enquiry). F. W. Goodenough, Dr. F. W. 

Edridge Green, E. T. Swinson, Lieut. S. R. Mullard, R.N.V.R.. Mrs. M. A. 

Cloudesley. Breretmi. A. Cunnington. J. G. Clark. A. P. Trotter. J. W. Barker. 

J. S. Dow, L. Gaster (18). 

Mar. 22 Fluorescence and Phosphorescence and their C/se to Produce 

Luminous Effects. By F. Harrison Glew, J. S. Dow, Arthur 

Blok. (4) 


List of Papers read before the Illuminating Engineering Society — (continued) : — 

May 15 Economies in Lighting in Relation to Fuel Saving. (5) 
Dec. 18 Presidential Address. By A. P. Trotter. 

Jan. 15 Ten Years of Illuminating Engineering. Its Lessons and Future 

Prospects. By L. G aster. (6) 
Feb. 26 A Survey of Methods of Directing and Concentrating Light. By 

Lt.-Commander Haydn T. Harrison. (13) 
April 16 Light and Vision, The Physiology of the Retina. By Prof. W. M. 

(Co-operation of Physiologists and Ophthalmists specially invited.) 
Discussed by : — 

E. Treacher Collins (President of the Ophthalmologics] Society), Sir J. Herberl 
Parsons, Dr. F. W. Edridge Green, Dr. .hums Kerr, Lieut. -Col. K. H. Elliott. 
Dr. J. F. Crowley, 8. Taylor, R. P. Howgrave Graham, A. P. Trotter, L. Gaster, 
W. C. Clinton, J. 8. Dow (1-'). 

May 14 Recommendations on Economy in Lighting. (9) 

Dec. 19 Photometric Apparatus for Measuring the Illuminating Value of 
Fluctuating Sources of High Candlepower (Flares, Parachute 
Lights, etc.). By A. P. Trotter. 
Some Photometric Tests of the Brightness of Radioa< tiyi: Self- 
Li minous Materials. By W. C. Clinton. 
Discussed by : — 

W. C. Clinton, .1. 8. Dow, C C. Paterson, Capt. G. Cray (M.o.M. Chemical War- 
fare Dept.), i". !•'. 8, Bryson (M.o.M. Optical Munition ami Glassware Supply), 

F. Harrison Clew, J. W. T. Walsh. A. Blok, Mrs. Hertha Ayrton, L. Gaster, 
A. L. Landau (11). 

Jan. 21 Modern Practice in Officio Lighting. I'.v A. Wise. (11) 
Feb. 25 Some Notes on Railway Lighting and Its Maintenance. By A. 

(Co-operation of Railway Engineers specuilhi invited.) 
Discussed by : — 

Haydn T. Harrison, J. H. Haigh (Lancashire and Yorkshire Railway), A. H. 
Stevens (London and North-Western Railway), P. Whvsall (Underground 
Electric Railways, Ltd.), 11. 1'erkin (Great Central Railway), F. W. Coodenough, 
A. Wise, H. E. Roberts (Soufch-Eastern and Chatham Railway), A. P. Trotter, 
L. Caster, H. I. Bond (London and South- Western Railway), N. W. Prangriell, 
E. S. D. Moore (London and North -Western Railway), M. Macdonald (Great 
Western Railway), C. R. Williams (15). 
April 8 The Art of Stage Lighting. By J. B. Fag an (Royal Court Theatre). 

(Meeting arranged in co-operation with the "Critics' Circle" of the 
Institute of Journalists.) 
Discussed by : — 

William Archer, T. J. Digby, G. E. Morrison (Chairman, " Critics' Circle "), 
N. R. Booth, Mrs. K. Searle, N. McDermott (Everyman Theatre), J. W. T. Walsh, 
Howgrave Grahim, Lane Crawford (Britannia Theatre), W. G. RafTe, J. Darch, 
A. P. Trotter, L. Gaster, G. A. Applebee, J. S. Dow, Gordon Craig (16). 
May 30 The Gas-Filled Lamp and its Effect on Illuminating Engineering. 
By F. W. Willcox. (15) 

(Meeting arranged in co-operation with the Electric Contractors' 
Association, the Association of Supervising Electricians, and the 
Association of Engineers in charge.) 
June 24 Street-lighting Reconstruction Problems. By L. Gaster. (7) 
Nov. 25 Introductory Meeting to Session : — 

Lambert and Photometry. By A. P. Trotter. 

Report of Committee on Progress in Lamps and Lighting 

The Sheringham Daylight. By L. C. Martin. 
New Form of Pointolite Lamps. By P. Freedman. 
A New Form of Illumination Photometer. By Haydn T. 
Dec. 16 The Art of Camouflage. By Capt. W. A. Howells, O.B.E. (6) 


List of Papers read before the Illuminating Engineering Society — (continued) : 

Jan. 27 Colour Matching by Natural and Artificial Light. By L. C. Martin. 
Discussed by : — 

A. E. Bawtree, Miss P. E. Baker. G. Herbert, A. S. Jennings, Dr. J. F. Crowley, 
J. H. Sutcliffe, AVm. Wallace. F. E. Lamplough, A. P. Trotter, G. Sheringham', 
L. Gaster, R. Leasing, E. R. Grills. Prof. W. M. Gardner. D. Patterson, M. L. m' 
Luckiesh, N. Macbeth, and J. S. Dow (18). 

Feb. 24 Lighting Conditions in Mixes with Special Reference to the Eye- 
sight of Miners. By Dr. T. Lister Llewellyn, Dr. H. S. Elworthy. 

(Co-operation of Medical Profession, Managers of Collieries, etc.) 
Discussed by : — 

Dr. J. S. Haldane. R. Annitage, M.P., Dr. F. Shufflebotham, E. Fudge (Secretary. 
Home Office Committee on Miners' Lamps), E. A. Haihvood, J. George, Dr.' 

D. L. Davis, T. Harrison Butler, Dr. C. F. Harford, V. V. Pass. G. H. Pooley! 
Bernard Cridland, A. L. Whitehead, N. Bishop Harman, L. Gaster, Sir Jchn H. 
Parsons (Chairman), Sir Geo. Berry, Sir Josiah Court, Dr. Geo. Maekay 
S. Nettleton. A. P. Welch. C. S. Percival. Dr. J. A. Wilson, Dr. L. Buchanan' 
H. F. Joel, Dr. M. Stassen (26). 

Mar. 30 Motor-Car Headlights in Relation to Traffic Requirements Bv 

J. W. T. Walsh. (18) 
April 20 The Artificial Lighting of Churches. By J. Darch. (9) 
May 11 Recent Developments in Types of Portable Cinema Outfits Bv 
Capt. J. W. Barber, C.B.E. 
Discussed by : — 

Dr. James Kerr, F. R. Goodwin (President of the Cinematograph Exhibitors' 
Association), Major A. Cooper-Key (Chief Inspector of Explosives, Home Office), 

E. Ridley (London Fire Brigade), J. C. Elvv, A. Blok, A. L. Roberts, L Gaster 
J. S. Dow (8). 

Dec. 14 Introductory Meeting to the Session devoted to Reports, Progress and 
Novelties in Illumination 

Reports on Progress in Gas and Electric Lamps and Lighting 

Small Gas-filled Lamps with Opal Bulbs. By E. Staines. 
Developments in the Sheringham Daylight. By Major A. 

Neon Lamps for Low Voltage Circuits. By J. S. Dow. 
A Foot-candle Meter. By J. S. Dow. 
The Lighting of Railway Time-Tables. By A. Cuxmngtox. 


Jan. 18 The Use and Abuse of Light for Kinema Film Production. Bv 
J. C. Elvy. 

(In co-operation with Ma)iagers of Kinema Studios, Kinema Experts, etc. ) 
Discussed by : — 

Sir Jchn H. Parsons, W. Day, A. G. Way, F. J. Hawkins, H. A. Carter, R. F. 
Boardman, Rt. Hon. G. H. Roberts. M.P.. A. Lugs, Capt. P. Kimberley, Capt 
J. W. Barber, C. Bennett, H. M. Lomas, S. Rowson, P. King, T. W. Armes 
L. Gaster, Sir William M. Bayliss, W. E. Bush, W. Krause (19). 
Feb. 24 The Use of Light as an Aid to Publicity (15) : — ■ 

(a) The Show Window and Spectacular Lighting. By Capt. E. 

(b) Illuminated Signs. By E. C. Leachman. 

Mar. 17 Motor-Car Headlights : Ideal Requirements, and Practical Solu- 
tions. By Major Garrard. (11) 
April 26 Ship Lighting in Relation to Safety, Comfort and Efficiency. By 
W. J. Jones. 

(Co-operation of representatives of the Admiralty, the Royal Navy, and 
the Mercantile Marine Service Association invited.) 
Discussed by : — 

F. P. Fletcher (Elec. Eng. Dept.. Admiralty). S. H. Callow. Capt. Colin Nicholson 
(Mercantile Marine Service Association), J. W. Elliott, Lt.-Com. J. W. A. Waller 
R.N., Capt, Collier, P. J. Waldram, Capt. A. L. Taylor. C. L. Matthews, C. E.' 
Greenslade, J. Freeth, A. M. Currie, C. H. Wordingham, L. Gaster (14). 


List of Papers read before the Illuminating Engineering Society — (continued) :— 

May 31 The Use of Light as an Aid to Various Games and Sports. By J. S. 

Dow. (7) 
Nov. 15 Introductory Meeting to the Session devoted to Reports, Progress, and 
Novelties in Illumination. 

Report on Progress in Lamps and Lighting Appliances. 

Fluorescence of Gems by Ultra-Violet Light. By W. J. Jones. 

New Types of Industrial Lighting Reflectors. By G. Campbell. 

Improvements in the Sheringham Daylight. By S. H. Groom. 

Chance's Daylight Glass. By F. E. Lamplough. 

The Grubbe " Non-Dazzle " Headlamp. By J. Armstrong. 

The Whitehead Headlight. By \V. J. Jones. 

Discharge (Neon) Lamps. By H. A. Carter. 

Developments in Luminous Signs. By E. T. Ruthven Murray. 

Luminor Signs. By Major W. C. AMCOTT8. 


Engineering. By W. J. Sandeman. 
Discussed by : — 

A E. Broadberry, A. Cnnnington, A. H. Stevens. V. W. Goodenoogh, L. Caster, 

P. -J. Waldiam/ A. E. Fry, \V. J. Jones, A. J. Whytc, L. M. Tye (10). 


Jan. 31 The Use ok Light AS an Aid to Aerial Navigation. By Lt.-Col. 
Blandy, D.S.O. 

(Joint Meeting with the Royal Aeronautical Society.) 
Discussed by : — 

Major-Gen. Sir Frederick Sykes. G.B.E., K.C.B.. C.M.G. (Controller^ Jcncral of 
Civil Aviation. Chairman), Col. Mervyn O'Gorman, Major-Gen. Sir Sefton 
Brancker, K.C.B., Sir Acton Blake (Deputy-Maoter of Trinity House). Haydn T. 
Harrison. T. E. Ritchie, Col. Gold (Meteorological Depfc., Air Ministry). 
P. J. Waldiam. A. (J. Watson, Lt.-Col. C. H. Sylvester Evans Major J. P. 
Ashley Waller (11.) 
Feb. 28 Industrial Lighting ; Ideal Requirements (Legislative and other- 
wise) and Practical Solutions. By L. Caster. (10) 
Mar. 27 Lighting of Public Buildings. By Dr. E. H. Rayner, J. W. T. Walsh, 
and H. Buckley. 

(Joint Discussion arranged with the Royal Institute of British 
Discussed by : — 

(apt. W. J. Liberty, F. A. Llewellyn (H.M Office of Works), P. J. Waldiam. 
Major H. C. Gonton (Post Office, Eng. Dept.), CL A. Baker (Elee. Engineer, 
L.C.( .). (i. Campbell, Haydn T. Harrison, A. Connington, A. G. Ramsey (H.M. 
Office of Works), A. C. Fallot (H.M. Office of Works), C. H. Burt, K, Langton 
Cole, A. E. Bullock, J. W. Jones (14). 

April 27 The Use of Light in Hospitals. By J. Darch. 

(Joint Meeting with the Royal Society of Medicine — Sections of 
Surgery and Ophthalmology.) 

Discussed by : — 

C. C. Choyce, W. T. Holmes Spicer, Conrad Beck, J. B. Reiner, A. Wilson, 
F. C. Raphael, J. W. Elliott, W. J. Jones, E. W. Johnston, L. Gaster, Major 
J. P. Ashley Waller (11). 
May 31 Annual Meeting. Presentation of Council's Report for Session and Address 
by the President (Sir John Herbert Parsons, C.B.E., F.R.S.). 

jjB. I n the case of subjects on which much difference of opinion exists, or where the co- 
operation of corresponding members, kindred societies, or experts outside the ranks of the Society 
was secured, we are including the names of those who joined in the discussion, in order to illustrate 
the wide circle of exerts interested in the work of the Society.— Ed. 


JHuminattng Engineering Society 

(Founded in London, 1909.) 

National Illumination Committee of Great Britain. [Reports issued 1922.] 

Mr. A. P. Trotter, Mr. L. Gaster, Mr. F. W. Goodenough, Dr. J. Kerr, Mr. C. C. Paterson, 
representing The Illuminating Engineering Society. 

Mr. F. Bailey, Mr. W. C. Clinton, Mr. K. Edgcumbe (Chairman), Mr. Percy Good, Mr. Haydn 
T. Harrison (Hon. Secretary), Prof. J. T. MacGregor Morris, representing The Institution of Electrical 

Mr. J. Abady, Mr. W. J. A. Butterfield, Prof. H. G. Colman, Mr. J. G. Clark, Mr. R. Watson, 
representing The Institution of Gas Engineers. 

Sir Joseph E. Petavel, Mr. J. W. T. Walsh, representing The National Physical Laboratory. 

Representatives of the Committee on the Executive Committee of the International Com- 
mission on Rlumination : — Mr. Leon Gaster and Mr. R. Watson. 

Joint Committee on the Standard Specification for Street Lighting. [Report Issued 1913.] 

Mr. W. H. Patchell (Chairman), Mr. F. Bailey, Prof. J. T. McGregor Morris, Mr. K. Edgcumbe, 
Mr. S. L. Pearce, Mr. S. Z. de Ferranti, Mr. H. F. Proctor, Mr. Haydn T. Harrison, representing 
The Institution of Electrical Engineers. 

Mr. W. DoigGibb (resigned December, 1911), Mr. S.Y. Shou bridge, Mr. R. Watson, representing 
The Institution of Gas Engineers. 

Mr. E. J. Elford, Mr. T. W. A. Hayward, Mr. G. F. Carter, Mr. E. B. B. Newton, Mr. N. Scorgie, 
representing The Institution of Municipal and County Engineers. 

Mr. L. Gaster, Mr. J. W. Ife, Mr. F. W. Goodenough, Mr. A. H. Seabrook (resigned November, 
1911), Mr. A. P. Trotter, representing The Illuminating Engineering Society ; Mr. J. W. Bradley 

Special Joint War Committee on Testing the Illuminating Power of Flares, Star Shells, 
etc. [Reports issued 1917, 1918.] 

Mr. A. P. Trotter (Chairman), Mr. L. Gaster (Secretary), Mr. J. G. Clark, Mr. W. C. Clinton, Mr. 
J. S. Dow, Prof. J. T. McGregor Morris, representing Tfie Illuminating Engineering Society. 
Mr. A. Blok, representing The Ministry of Munitions (O.M.G.). 
Mr. Maurice Blood, representing D.I.S.A.A., Royal Arsenal, Woolwich. 
Capt. G. H. Wicks, representing The Chemical Warfare Dept., Ministry of Munitions. 

Special Joint War Committee on Testing the Brightness of Radioactive Self-luminous 
Materials. [Report issued 1918.] 

Mr. L. Gaster (Chairman), Mr. W. C. Clinton, Mr. J. S. Dow (Secretary), representing The 
Illuminating Engineering Society. 

Mr. A. Blok, representing Ministry of Munitions (O.M.G.). 

Joint Committee on School Lighting.* [Reports issued 1913, 1914.] 

Asst. Prof. W. C. Clinton, Mr. J. Darch, Mr. J. S. Dow, Mr. L. Gaster (Secretary), Mr. F. W. Good- 
enough, Dr. H. R. B. Hickman, Dr. J. Kerr (Chairman), Mr. W. R. Rawlings, Mr. T. E. Ritchie, 
Mr. A. Stokes, Mr. S. E. Thornton, Mr. P. J. Waldram, representing The Illuminating Engineering 

Dr. R. S. Clay, representing the Association of Technical Institutions. 

Dr. J. H. Vincent, representing the Association of Teachers in Technical Institutions. 

Mr. E. S. Mortimer, representing the London Teachers' 1 Association. 

Dr. E. H. Nash, representing the Medical Officers of Schools Association. 

Mr. N. Bishop Harman. 

Joint Committee on Library Lighting.* [Report issued July, 1913.] 

Dr. W. M. Bayliss, Mr. J. G. Clark, Mr. J. S. Dow, Mr. J. Eck, Mr. L. Gaster (Secretary). Mr. 
S. Hamp, Mr. Haydn T. Harrison, Mr. Chas. W. Hastings, Mr. B. H. Jenkinson, Mr. V. H. Mackinney, 
Mr. N. W. Prangnell and Mr. A. P. Trotter (Chairman), representing The Illuminating Engineering 

Mr. H. Bond, Mr. J. Duff Brown, Mr. B. Carter, Mr. Hopwood, Mr. H. Jones. Mr. R. Peddie, 
and Mr. H. R. Tedder, representing the Library Association. D 

216 THE ILLUMIXATIXc ! ENGINEER (jtjly 1922) 

Joint Committee of Inquiry on Eyestrain in Cinema Theatres and its Prevention.* 

[Report issued 1920.] 

Mr. A. Blok, Asst.-Prof. W. C. Clinton, Mr. J. S. Dow, Mr. L. Gaster (Secretary), Mr. F. W. 
Goodenough Mr. Haydn T. Harrison, Prof. J. T. McGregor Morris, representing The Illuminating 
Engineering Society. 

Col. J. H. Parsons, C.B.E. (Chairman), Mr. Stephen Mayou, Mr. W. H. McMullen, O.B.E., 
and Mr. Bernard Gridland, representing The Council of British Ophthalmologists. 

Prof. W. M. Bayliss, Dr. W. MacDougall, Prof. C. S. Sherrington, Prof. C. Spearman, repre- 
senting The Physiological Society. 

Mr. E. Ridley (Inspection Dept., London Fire Brigade, L.C.C.),Dt. James Kerr (Medical Research 
Officer, Public Health Daat., L.C.C.), (Deputy Chairman), Dr. C. W. Kimmins (Chief Inspector, 
Education Officer's Dept., L.C.C.). 

.Mr. F. G. Goodwin, Mr. A. E. Newbould, Mr. J. W. Barber, representing the Cinema Industry. 

Joint Committee on Railway Lighting.* 

Lieut. -Col. F. A. Cortez Leigh (London and North Western Railway), Chairman, Mr. J. S. Dow, 
Mr. L.Gaster, .Mr. F. W. Goodenough, Mr. A. Stokes, Mr. A. Cunnington (London and South Western 
Railway), Secretary, representing The Illuminating Engineering Society. 

Mr. A. R. Cooper (Underground Railways), Mr. Wood (North British Railway), Mr. Roger T. 
Smith (Great Western Railway), representing The Association of Railuay Electrical ami Tdegraph 

Committee on Progress in Lamps and Lighting Appliances.* [Reports annually.'] 

Electric : — Mr. S. H. Callow (Chairman), Mr. J. E. Edgecombe, Mr. J. W. Elliott (Secretary). 
Mr. J. Y. Fletcher, Mr. F. W. Willcox. Gas:— Mi. J Bridget (Chairman), Mr F. J. Gould, 
Mr. G. Hands, Mr. W. Mattock, Mr. F. <\ Tillev (Secretary). 

Joint Committee on Kinema Studio Lighting.* 

Mr. A. Blok. Mr. .1. s. Dow, Mr. LG i bay), Mr. F. F. Lampiough, Mr. H. M. Lomas, 

Prof. J. T. MacGregor Moms. Mi. I'. Twyman, representing 77<> Illuminating Engineering Society. 

Capt. J. W. Barber, C.B.E. (London Film Co.), Major Bell (Famous Lasky British Produc- 
tions, Ltd.) Lt.-Col. A. C. Bromhead, Gaumont Co., Ltd. (Deputy Chairman), Capt, ('. M. Hepworth 
(Hepworth Picture Plays, Ltd.), representing Incorporated Association of Ki»< matograph 
Man ufact u rers. 

Sir John H. Parsons, C.B.F., F.H.S. (Chairman), Mr. A. B. Oidhmd. Mr. S. Mayou. Mr. W. H. 
McMullen, representing Council of British Ophthalmologists. 

Sir William M. Bayliss, F.B..S. (Deputy-Chairman), Dr. H. Hartridge, Prof. C. Spearman, 
representing Physiological SocU ty. 

Mr. A. C. Banfield (Deputy-Chairman), Mr. F. C. Toy, representing Royal Photographic Society. 

Dr. T. Slater Price, Mr. F. C. Toy. representing British Photographic Research Association. 

Joint Committee on Motor Car Headlights.* 

Mr. J. S. Dow, Major A. Garrard, Mr. L. Gaster (Secretary). Capt. E. Stroud, representing 
Illuminating Engineering Society. 

Mr. Worbv lieaumon (Chairman), representing Royeil Automobile Club. 

Mr. H. S. Rowell, representing Research Association of the British Motor and Allied Manu- 

Col. D. J. Smith, representing Institution of Automobile Engineers. 

Mr. David Smith, representing British Scientific Instrument Research Association. 

Mr. G. W. Watson, representing Commercial Motor Users' Association. 

Mr. J. E. Edgecombe, representing Electric Lamp Manufacturers' Association of Great Britain, 

Mr. S. Mayou. representing Council of British Ophthahnologists. 

Dr. H. Hartridge, representing Physiological Sod, ty. 

Standing Committee on Photometry and Allied Subjects.* 

Mr. A. Blok, Mr. J. G. Clark, Mr. W. C. Clinton, Mr. J. S. Dow, Mr. K. Edgcumbe, Mr. L. 
Gaster (Secretary), Mr. Haydn T. Harrison, Mr. W. J. Liberty, Prof. J. T. MacGregor Morris 
(Chairman), Mr. A. Stokes, and Mr. A. P. Trotter. 

Joint Committee on Hospital Lighting. 

(In course of formation.) 

* The President, Hon. Secretary and Assistant Hon. Secretary are ex-officio members of all 


Committees as at present constituted have power to co-opt or to call as witnesses members of the 
Society or others whose knowledge or txperiena would be of dim fit in their inquiries. 


INDEX, July, 1922. 


Editorial. By L. Gaster 183 

Factories and Workshops, Third Report of the Home Office Departmental 

Committee on . . . . . . . . . . . . . . . . 197 

^Humiliating Engineering Society— 

(Founded in London, 1909) 

Account of Annual Meeting . . . . . . . . . . . . 187 

Report of Council for the Session, 1921-22 189 

Presidential Address by Sir John Herbert Parsons, C.B.E., F.R.S. 194 

Special Section : — 

The Illuminating Engineering Movement in England 

The Work of the Illuminating Engineering Society 

List of Officers and Members of Council 

List of Papers and Discussions (1909-1922) 

List of Committees and Reports issued 

Future Developments in Illuminating Engineering 


Future Developments in Illuminating Engineering. 

From the foregoing it is evident that the Illuminating Engineering Society, during 
its twelve years of existence, has more than justified the hopes of those responsible 
for its inauguration in 1909. Its work has received general recognition and the 
foundations of future usefulness and prosperity have been truly laid. 

But the time is now ripe for energetic development of its programme on a much 
greater scale. Considering that its work is carried on mainly by voluntary effort, 
the good results so far obtained merely show how much greater might be its 
influence if support were available for further development. 

While its work has penetrated far afield, not enough has been done to develop 
illuminating engineering in the provinces, or in the Colonics and Dominions which 
furnish a most fruitful field for influence. Again, while many useful researches have 
been initiated, work in this direction has been restricted by the limited resources 
available for encouraging experiments. Another limiting factor has been the great 
increase in the costs of printing and publication, which have made it necessary to 
curtail the size of the journal. In the future it is hoped to make the Journal an 
even more useful publication by including records of developments in illuminating 
engineering throughout the world and special articles by experts on selected subjects 
on the lines follow ed in early issues. 


The chief additional steps desirable in the near future may be summarised as 
follows : — 

(a) Organisation of extensive propaganda with a view to interesting 
Municipalities, Public Bodies, Educational Authorities, Owners of Factories 
and Workshops, etc., in illumination, and bringing about a better appreciation 
of the value of good lighting. 

(b) Arranging lectures and demonstrations in various parts of the country, 
for the benefit both of those technically concerned with lighting (architects, 
contractors, etc.), and important classes of consumers. 

(c) Forming a fund for researches, and especially aiding the experiments 
to be conducted by the Society's various committees. 

(d) Expanding the size of the Journal by including special contributions 
on selected subjects, and preparing additional pamphlets for propaganda purposes. 

(e) The formation of local sections of the Society in the provinces, where 
meetings of special local interest would be arranged. 

(f) The initiation of propaganda in the Colonies and Dominions where 
at present little is being done by this country to develop a demand for better 
lighting, and where, ultimately, sections affiliated to the British Society would 
eventually be built up. 

(g) Co-operation with illuminating engineering societies in foreign countries 
and arrangements to assist the participation of the Society in any steps that 
may be taken in the future towards the treatment of illumination on an 
international basis. 

Hence, while the illuminating engineering movement will continue to advance, 
the rate of progress depends necessarily on the financial assistance and co-operation 
which the Society receives. Expenditure on propaganda and research would be 
well repaid by a corresponding rapid acceleration of the Society's programme. In 
order to develop the movement to full fruition, greater assistance should be given by 
all who are interested in the lighting industry, and have benefited by the educational 
movement in favour of better fighting. 

Over £20,000 have been expended on the movement during the last fourteen 
years. Now the moment is opportune to present a claim for further support. The 
initial pioneering work has been done, but the Society needs a greatly increased 
membership and adequate funds for propaganda and research in order to take full 
advantage of the position created and encourage the carrying into practice on a large 
scale of the principles that have now been established. 

Those who have benefited from the movement and are desirous of promoting 
further progress can do so by filling in the accompanying form for the purpose of :— 

(1) Becoming members or associates. 

(2) Becoming supporters, i.e., by paying a special contribution towards 
the propaganda work of the Society. 

(3) Giving donations to form the nucleus of a special fund for research. 

Further particulars can be obtained on application to Mr. L. Gaster, Hon, 
Secretary, 32, Victoria Street, London, S.W.I. 




£:OjTe*cl- £>\s J 






illuminating Engineering Society. 

(Founded in London, 1909.) 


Tel. No. Victoria 5215. 


Scientific and Industrial Research. 

The Report of the Committee of the Privy Council for Scientific and 
Industrial Research for the year 1921-22 is, as might be expected in the 
present circumstances, largely concerned with questions of expenditure 
and finance. In their former report attention was drawn to steps already 
taken to curtail provision in the interests of economy. While we must 
all regret that such restrictions are found necessary it is gratifying to note 
that the Committee on National Expenditure did not find it necessary 
to recommend any reduction in the estimates of the Department, beyond 
that which it had itself proposed. 

Fortunately, while the curtailment of expenditure has involved a 
slowing down of the research programme it has not interrupted work 
already in hand. This work has already reached considerable dimensions. 
Research Boards are at work on such problems of national value as fuel, 
food investigation, forest products, geological survey, etc., and there are 
a large number of special committees conducting researches, many of 
which appear to have already done excellent work. A feature of interest 
is the formation of co-ordinating Boards for Chemistry, Physics, Engineer- 
ing and Radio Research, whose function it is to co-ordinate researches 
made in various quarters and prevent overlapping of work. Their ser- 
vices should be conducive to economy. The number of industrial research 


associations which have received licences from the Board of Trade is 24. 
and of these 22 are in actual operation. Special grants have also been 
given to various scientific bodies and individual research workers. We 
are glad to note that the number of applications received (544) and awards 
of grants (280) to such workers shows an increase. As this item must 
form only a small part of the total expenditure we earnestly hope that 
efforts at economy in this department will not be unduly severe. It is 
of the highest importance that the formation of a nucleus of research 
workers throughout the country should be built up and there is no doubt 
that in the past the country has suffered from an inadequate supply of 
skilled experimenters in various industries 

In addition the Department is now responsible for the support of the 
National Physical Laboratory, which received approximately £190,024 
out of a total expenditure from public funds during 1921-22, of {..V,' S ,55-- 
The Department has been the means of bringing scientific training within 
the reach of many who would otherwise be unable to develop their Latent 
capacity for research and its influence in fostering the spirit of scientific 
inquiry is a national asset. 

The report deals in a very practical manner with the query, " What 
is the country receiving in return for this annual outlay ? " It is able 
to point to several direct benefits. Thus the routine work of the National 
Fronde lank is saving shipbuilders who consult it 2 to per rent, of their 
coal bills, and its investigations for the Admiralty and Air Ministry cannot 
be evaluated in terms of money. Valuable industrial results and economies 
in the design of kilns have 1 ecu effected through the research of the British 
Portland Cement Research Association, in one case Leading to .1 reduction 
in the running hours of the mills and the accessary lal our of .;.;', per cent. 
The British Scientific Instrument Research Association has developed 
new polishing powders and abrasive agents that are being made on a large 
scale and are proving extremely useful in industry. It is of course too 
early to expect final results from some of the Boards dealing with projects 
of national importance such as food investigation and fuel research ; 
it is hoped, however, that the researches conducted by such boards will 
ultimately lead to results which will far outweigh the expenditure 

The cumulative influence of these research associations on the 
industries with which they are concerned must he considerable. While 
material benefits are recorded in many cases the indirect influence of the 
fostering of the spirit of research in industry should lead to most valuable 
results in the future. We have previously referred to the recent record 
of work at the X.P.L., which includes various researches in the field of 
illuminating engineering (notably in connection with industrial lighting 
and the lighting of public buildings) and to the erection of a special build- 
ing to facilitate experiments on illumination. We are glad to see that the 
laboratory is now receiving more generous support. 

It appears that over £800,000 of the original million fund remained 
unexpended on March 31st, i()22. so that the maintenance of the work 
of the Department is assured for some years to come. National economy 
will doubtless remain a pressing problem during these coming years. But 
if, as already appears probable, the Department can justify its existence 
as an indispensable national asset, we hope that some means of ensuring 
the continuity of its work will be found. 


Scientific Progress and Publicity. 

We have frequently referred to the importance of publicity being 
given to important work by technical and Governmental committees, 
pointing out that much valuable matter is often lost in bulky publications 
and possibly only brought to the notice of a few of those who might benefit 
by a knowledge of the conclusions arrived at. We have emphasised the 
desirability of brief and readable abstracts, giving the essential points 
of such inquiries, being distributed amongst the daily and technical Press, 
and pointed out that in the Scientific and Technical Circle of the Institute 
of Journalists there exists a body in a very favourable position to be of 
service in this connection. It is not sufficiently realised that the carrying 
out of an investigation, however admirable and important it may be, is 
only a part of the problem. It is at least equally important that the results 
obtained should be widely known. 

It is here that Government Departments and scientific and technical 
bodies so often fail. The machinery for giving publicity to the reports of 
committees is in many respects imperfect and much of their value is lost. 
A relatively small expenditure on efforts to secure publicity would be 
well repaid. 

The matter is of special consequence to the Department for Scientific 
and Industrial Research, whose future depends not merely on a proper 
appreciation of the value of the work that the Department is doing but 
on a better public understanding of the general advantages of svstematic 
scientific method and research. As is truly remarked in the Report the 
benefits of extensive researches may only be slowly realised, and it is not 
always easy to impress on the public the value of the gradual permeation 
of industries with the scientific spirit, as a national asset. The most 
valuable form of propaganda at the moment is the dissemination of actual 
improvements and economies in industrial processes, the money value 
of which can be readily assessed. We would suggest, therefore, that the 
Department should make a special effort to collect from committees and 
research associations concrete instances of valuable results, and ultimately 
present a form of balance-sheet showing that these afford ample justification 
for the expenditure. Definite information of this kind would, we feel 
sure, be readily accepted for publication both in the daily and technical 

We observe with pleasure that the Department is already aiding the 
dissemination of scientific knowledge in another way, i.e., by making 
grants towards the publication of scientific researches. One notable in- 
stance was the contribution given towards the expense of publishing a 
specimen copv of a Journal of Scientific Instruments, for which a need 
doubtless exists. We certainly think that as soon as circumstances allow, 
the Department might favourably consider the question of giving some 
assistance to journals that are engaged in the difficult task of conveving 
scientific and technical information to the public, particularly those that 
act as the official organs of scientific societies. Owing to the increased 
cost of printing and publication the position of such journals is very diffi- 
cult, and the work that they are doing, though rendered possible by private 
enterprise, is surely of value to the nation. We understand that the 
Conjoint Board of "Scientific Societies has made strong representations to 
the Department on this subject and it appears to us that this valuable 
educational channel, which brings information before precisely those people 
who are interested in it, deserves every support. 


Improvements in Street Lighting. 

Now that we are approaching the winter season public lighting 
authorities would do well to review their present arrangements for street 
lighting and consider what improvements are absolutely necessary. It 
is generally admitted that there is still a good deal of leeway to be made 
up, especially in view of the fact that in many districts practically nothing 
in the way of renovation was done during the war. In present circumstances 
the claims of economv must be considered, and authorities may naturallv 
be reluctant to embark upon extensive alterations. But there are doubt- 
less cases in which gas burners or electric fittings have become worn out 
and demand renewal and some improvement is imperative ; in such 
circumstances it would be well to consider whether an improvement could 
not be made by the introduction of more up-to-date appliances, and possibly 
an economy as well ? 

An interesting case in point is afforded by the experience of Xewcastle- 
on-Tyne, where a report from the City Lighting Superintendent, summaris- 
ing the result of improvements carried out last year, was recently presented. 
It had become evident that, owing to depreciation during the war period, 
about 1,000 burners needed to be replaced, and the opportunity was taken 
to introduce more up-to-date appliances. Superheated inverted gas burners 
in place of the existing upright types were accordingly substituted. 

The advantages of the inverted superheated " cluster " fittings were 
fully described in Mr. Sandeman's paper before the Illuminating Engineer- 
ing Society in December last. They combine greater durability with 
higher efficiency and in particular enable a substantial saving on mantle 
maintenance to be made. This is fully borne out by the data presented 
in regard to the Newcastle installation. According to the report the 
annual cost of replacing inverted burners has been only £910 as compared 
with £3,633 in the preceding year. It has also been found possible to 
effect a material saving in gas consumption. The annual saving from 
both sources exceeds £5,000 a year, so that the total capital cost of the 
conversion (£2,431) has been recovered in less than six months. 

Public authorities throughout the country, even in these days of 
enforced economy, have every inducement to make changes which bring 
about results such as these, and there is no apparent reason why obsolete 
burners with upright mantles should still be found in use for public lighting 
in some districts. 

It is stated in the report that, in addition to the economv obtained, 
the lighting has been much improved, and this is illustrated by photo- 
graphs taken under the old and new conditions. As each upright burner 
has been replaced by an inverted one, there is no reason to doubt this 
improvement, though we think that the report would have been even 
more valuable if exact tests of the illumination under the old and new 
conditions had been furnished. The point to be noted is that improvements 
in lighting do not necessarily involve higher running costs. In times 
such as these, obsolete and inefficient devices should be resolutely scrapped 
in the interests of economy as well as better lighting. 

As the need for rigid economy becomes less pressing the opportunities 
for more scientific and artistic methods of street lighting will doubtless 
arise. The moment thus seems ripe for a survey of the whole problem, 
which was last considered by the Illuminating Engineering Society shortly 
before the war. We are therefore glad to observe that the Society is 
arranging for a discussion to take place early in the next session. 

Leon Gaster. 




(Affiliated to the International Commission on Illumination.) 

Constituted by Co-operation of : — 

Representatives nominated to serve on the Committee for the year 1922 
Jacques Abady (c) F. W. Goodenough (a) 


J. G. Clark (c) James Kerr (a) 

W. C. Clinton (b) J. T. MacGregor-Morris (b) 

Harold G. Colman (c) Clifford C. Paterson (a) 

Kenelm Edgcumbe (b) Sir Joseph E. Petavel (d) 

Leon Gaster (a) A. P. Trotter (a) 

Percy Good (b) J. W. T. Walsh (d) 

Robert Watson (c) 

(a) Nominated by the Illuminating Engineering Society. 

(b) Nominated by the Institution of Electrical Engineers. 

(c) Nominated by the Institution of Gas Engineers. 

(d) Nominated by the National Physical Laboratory. 

The Committee has made the following appointments : — 

Representatives of Great Britain on the Executive Committee of the International 
Commission on Illumination : — 

Leon Gaster and Robert Watson. 

Chairman : Major Kenelm Edgcumbe. 

V ice-Chairmen : Clifford C. Paterson and Robert Watson. 
Secretary and Treasurer : W. J. A. Butterfield, 

66, Victoria Street, 

London, S.W.I. 

Report of the Chairman for the Year 1921. 

Presented at the Special Annual Meeting of the Committee held on 2nd February, 1922. 

PARIS MEETING. were :— Major K. Edgcumbe, Mr. L. 

The most important event during the Gaster, Mr. C. C. Paterson, Dr. E. H. 

year was the plenary meeting of the Inter- Rayner, Mr. A. P. Trotter, Mr. J. W. T. 

national Commission on Illumination, held Walsh, and Mr. R. Watson. Mr. Percy 

in Paris from the 5th to the 8th July last. Good was, at the last minute, prevented 

Dr. Colman who, with Mr. Gaster, has from attending, 
been the Representative of the British A most excellent report of the proceed- 

National Committee on the Commission ings was prepared by Mr. R. Watson in 

since 1914, being unable to attend, Major the form of a paper presented to the 

K. Edgcumbe was appointed to take his Institution of Gas Engineers, and will 

place. The Members of the British Com- be published by that body in their Trans- 

mittee who attended the Paris Meeting actions. 



The principal features of the Inter- 
national Meeting may be briefly summar- 
ised as follows :— 

1. The adoption, on the recommenda- 
tion of the British Committee, of the 
"Internationa] Candle" as defined by 
the Standardising Laboratories of Great 
Britain, France, and the United States of 

2. The following terms, as well as their 
units, were defined : — ■ 

Luminous flux, illumination, and Lumin- 
ous intensity. 

The definitions adopted closely followed 
those proposed some years previously by 
M. Blonde], and although the British 
delegates were in disagreement with the 
latter on several points notably in treat- 
ing "' luminous flux " as a rate of flow 
instead of as an entity it soon became 
evident to them that international agree- 
meiit was only possible by the adoption 
of such conventions which, although 
admittedly ambiguous, had already come 
into somewhat extensive use. 

3. Discus-inns took place on various 
subjects, notably upon Heterochromatic 
and Physical Photometry, the lighting 

of factories. Schools, etc., and the avoid- 
ance of glare in aut >bile headlights. 

1. ( lommittees were a ppointed to deal 
with the following subjects, t he representa- 
tives of Greal Britain upon each being 
shown in brackets. 

Heterochromatic Photometry (Dr. E.H. 

Definitions and Symbols (Mr. J. W. T. 


Lighting of Factories and Schools 
(Mr. L. Gaster). 

Automobile Lighting (to be nominated 
by the British National Committee). 

5. It was decided to base the annual 
contribution to be made by each country 
upon its population instead of making it 
a fixed sum, as heretofore. The total 
income budgeted for was £600 per annum, 
of which the share of Great Britain, upon 
the above basis, is £113 10s. 

6. The 
appointed :- 


following office 


Dr. E. P. Hyde 


Vice-Presidents.. M. F. Roland 

M. G. Semenza 

Major K. Edgcumbe 
(Great Britain). 

Hon. Sec . . Mr. C. C. Patereon. 

(Creat Pritain). 

Assistant Sec. . . Mr. J. W. T. Walsh 
(Great Britain). 

M. 'I'h. Vautier, the retiring President, 
was unanimously elected an Hon. 
President, in recognition of his long and 
devoted work in connection with the 
< 'ommission. 

7. It was decided to hold the next 
meeting in 1924, New York being 
provisionally selected as the meeting 



In view of the decisions come to at the 
Paris Meeting it was uecessary for the 
Definitions provisionally drawn up by 
the British Committee to be somewhat 
modified. This was undertaken by the 
Nomenclature Sub-Committee, and after 
approval by the British National Com- 
mittee, the revised draft was circulated 
to the three constituent societies with the 
request that, in the event of any disagree- 
ment, they would communicate with the 
Hon. Secret a rv. No objections have been 
received, and the Institution of Electrical 
Engineers have already published the 
Definitions in their Journal. 

A list of the Definitions, as approved, 
form an Appendix to the present Report. 


During the year there have been seven 
meetings of the National Illumination 
Committee, as well as a large number of 
meetings of the Nomenclature Sub- 
committee. All these have been held at 
the offices of the Illuminating Engineering 
Society, and the best thanks of the Com- 
mittee are due to that Society, as well as 
to Mr. L. Gaster, the Hon. Secretary, for 
their kindness in this respect. 







{Appendix to the Eejjort of the Chairman for the Year 1921, presented at the Special Annual Meeting 
of the Committee held on 2nd February, 1922.) 


The definitions to which this note 
serves as an introduction have been 
drawn up by the National Illumination 
Committee of Great Britain, and embody 
the recent decisions of the International 
Commission on Illumination. They are 
intended to serve as a set of formal 
definitions of the principal terms at 
present in use in the science of photo- 
metry and illumination. 

The first four definitions refer to the 
fundamental quantities " luminous flux " 
and " luminous source " and their units. 
The whole set of definitions is, therefore, 
dependent on these and, in fact, it may 
be said that the whole system is based 
on these two fundamental conceptions. 

Although, in this country, the word 
"' flux " is used to denote a flow rather 
than a rate, the use of the term " luminous 
flux " has become so universal abroad 
that it is impossible now to adopt any 
other term for the rate of passage of 
radiant energy. The Committee's chief 
objection to the term is that it has 
frequently been loosely used in the past 
as if it represented the entity itself, and 
not, as it does in fact, a rate of passage 
of the real entity, viz., energy. It is true 
that since the velocity of propagation 
of this energy may be taken as constant, 
the rate of passage is proportional to 
something which may be conveniently 
looked upon .as an entity. In the same 
way electric current, which is the rate of 
passage of electricity, is almost invariably 
looked upon as an entity. Provided its 
real nature be kept in sight, there is much 
to be gained in conciseness of expression 
by using the word " flux " in the way 
proposed. Care must, however, be taken 
to preserve the distinction between 
luminous flux, as now defined, and energy. 

Actually, of course, emission or recep- 
tion of luminous flux is a rate of emission 
or reception of luminous energy, and is 
therefore analogous to power. The idea 
is brought out in the term " candle- 
power," proposed as a substitute for 
what has often been termed, in the past, 
" luminous intensity." Candlepower is, 
in reality, nothing but a rate of emission 
of (luminous) energy. It is therefore 
analogous to the horse-power of a motor, 
where the mechanical power produced 
is compared with the luminous flux. 
The term " candlepower " has been 
retained also as having the sanction of 
continued use, and because it links the 
name of the abstract quantity to the name 
of the concrete unit, the " candle." 
The term " luminous intensity " has been 
disco\iraged in this country as there is 
now a tendency to restrict the word 
" intensity " to a ratio in which the 
denominator is an area. There is no such 
restriction upon the use of the French 
word " intensite " which is therefore 
retained in the International Definitions. 

The terms used to denote the average 
value of the candlepower of a source, 
whether in all directions throughout 
the total solid angle of 4n- sterradians, 
or in all directions within a smaller 
defined solid angle, have been recast 
with the intention of making them more 
concise and, at the same time, more 

Illumination is the rate of reception 
of luminous energy over a given area, 
i.e., the reception of luminous flux by 
that area. The lux or met re -candle is 
thought preferable to the phot as^ the 
unit of illumination, since it is of the 
same convenient order of magnitude as 
the foot-candle, which is so commonly 



Brightness is of the same nature as 
candlepower, in that each denotes a rate 
of emission of luminous energy. It is 
therefore most reasonable to define 
brightness in terms of candles per unit 
area, a small area being adopted for 
such intense brightness as is met with 
in most self-luminous bodies, and a 
larger area for brightness of the order 
generally found in the case of illuminated, 
as opposed to self-luminous, bodies. 
Owing to the fact that the brightness of 
any surface, seen by the eye, depends on 
the candlepower per unit of apparent 
area, it is clearly sufficient to define the 
brightness of a surface in any direction 
as the candlepower per unit apparent area 
in that direction. It follows, from this, 
that a perfectly diffusing surface, i.e., one 
whose absolute candlepower varies as the 
cosine of the angle of emission, will have 
the same brightness whatever be tin- 
direction from which it is viewed. 

In the past, it has frequently been the 
practice to express brightness in terms 
of the brightness of a perfectly diffusing 
surface which reflects all the light it 
receives, and which is illuminated to the 
extent of one metre -candle or one 
foot-candle. This unit has been called 
the "equivalent metre-candle" or the 
"equivalent foot -candle " respectively. 
There are at least two objections to this 
practice. It tends to a confusion of 
ideas as between illumination and bright- 
ness, and it begs the question of the 
perfectly diffuse reflecting action of the 
surface in question, since tin- conception 
is, almost invariably, used to obtain the 
brightness as a simple product of the 
illumination and the reflection ratio. 
It appears, in fact, to be an attempt 
to avoid the recognition of the fact that 
the luminous flux from a completely 
reflecting and perfectly diffusing surface 
is not emitted equally in all directions, 
so that the candlepower of such a surface 
receiving one lumen is \ir candles. 

The various methods hitherto used 
for expressing the performance of a 
light source in terms of its output of 
luminous flux for every unit of electrical 
or chemical power consumed, received 
very careful consideration from the 
Committee. The term " efficiency " when 
applied to the ratio " watts/candles " 
is objectionable, since the numeric 
increases as the ratio " output/input " 
decreases. At the same time it 
was felt that to apply the term 
" efficiency " to any other ratio would 
inevitably lead to confusion for a con- 
siderable time to come. The ratio of 
the power supplied to the luminous 
source (expressed in watts or in British 

thermal units per hour) to the average 
candlepower (expressed in candles) has 
therefore been termed the " specific 
consumption " of the source, while the 
ratio of the luminous flux output 
(expressed in lumens) to the power input 
(expressed in watts or B.T.C.) has been 
called the '" specific output." The Com- 
mittee do not regard these terms as 
wholly satisfactory, but with the word 
" efficiency " so definitely ear-marked 
to denote " watts per candle," the 
position was felt to be one calling 
for compromise between ideals and 

The term " ratio " has been used in 
the definitions of reflection, absorption 
and transmission, as expressing more 
clearly than "' coefficient " the true 
nature of these numerics. In the 
definition of these ratios it is implied 
that, in addition to a particular ratio 
}>"inL r cinfincd to the case of light 
of some particular spectral distribution, 
it is also restricted to light incident at 
some definite angle, and, in the case 
"f the first and last, to a definite direction 
of the reflected or transmitted light. 
It is usual, in the case of those bodies 
which approximate to perfect diffusers, 
to make use of the term specific diffuse 
reflection to denote the ratio of the total 
reflected to the total incident flux. 
Similarly, for surfaces which approximate 
to perfect mirrors, the ratio of the 
reflected to the incident flux in the 
directions of the reflected and incident 
beams, respectively, is termed the 
" specific regular reflection." 

The Committee, feeling that at the 
present stage the most important con- 
sideration is to obtain agreement on 
fundamentals, has not yet proceeded 
to define such terms as " diversity 
factor," " window efficiency," " ex- 
posure," and others frequently used in 
illumination engineering. Neither have 
they attempted, at present, to deal with 
the definition of the various terms 
employed in colour specification, or in 
the study of the visibility of radiation 
and the mechanical equivalent of light. 

Definitions and Units. 

(1) Luminous flux is the rate of 
passage of radiant energy evaluated 
according to the luminous sensation 
produced by it. Since for all practical 
photometric purposes the velocity of 
light may be regarded as constant, 
luminous flux may be treated as an 
entity, and is so treated in the definitions 
which follow. 



(2) The unit of luminous flux is the 
lumen. It is equal to the luminous 
flux emitted per unit solid angle by a 
uniform point source of one international 

(3) A luminous source is one which 
emits luminous flux. A point source 
is one which subtends a negligibly 
small angle at the point from which it is 

(4) The luminous intensity or candle- 
power of a point source in any direction 
is the luminous flux emitted in that 
direction by the source per unit solid 

(5) The unit of luminous intensity or 
candlepower is the international candle. 
This unit is the outcome of agreement 
arrived at by the three National 
Standardising Laboratories of France, 
Great Britain and the United States 
of America in 1909. The unit has since 
that time been preserved by these 
laboratories by means of electric incan- 
descent lamps, and the laboratories are 
still responsible for its preservation. 

(6) The average candlepower of a 
luminous source is the average value 
of the candlepower in all directions. 
(This term is recommended in place of 
the term " mean spherical candlepower.") 
When it is desired to define the average 
value of the candlepower in a given 
zone or given hemisphere, this should 
be specified thus : " average candle- 
power (upper hemisphere)." 

(7) The illumination at a surface is 
the luminous flux reaching that surface 
per unit area. 

(8) The practical unit of illumination 
is the lux. It is the illumination at 
the surface of a sphere of one metre 
radius due to a uniform point source of 
one candle placed at its centre, i.e., 
it is equal to one lumen per square metre. 

If the centimetre be taken as the unit 
of length the unit of illumination is the 

lumen per square centimetre known as 
the phot. If the foot is taken as the 
unit of length, the unit of illumination 
is the lumen per square foot known as 
the foot-candle. 
1 foot-candle= 10-764 lux=r0764 milli-phot. 

(9) The brightness of a surface in a 
given direction is the candlepower per 
unit projected area of the surface in 
that direction. It is expressed either 
in candles per square millimetre or per 
square metre. 

(10) The specific output of an electric 
lamp is the ratio of the luminous flux 
to the power input. It is expressed in 
lumens per watt. The specific output 
of a source depending on combustion 
is similarly expressed in lumens per 
British thermal unit per hour. 

(11) The specific consumption of an 
electric lamp is the ratio of the power 
input to the average candlepower. It is 
expressed in watts per average candle. 
The specific consumption of a source 
depending on combustion is similarly 
expressed in British thermal units per 
hour per average candle. 

(12) The reflection ratio of a surface 
for radiant energy of given spectral 
distribution is the ratio of the luminous 
flux leaving the surface to the luminous 
flux incident thereat, both being 
expressed in lumens. (This quantity 
has hitherto been termed the "co- 
efficient of reflection.") 

(13) The absorption ratio of a body 
for radiant energy of given spectral 
distribution is the ratio of the luminous 
flux absorbed by the body to the 
luminous flux incident thereat., both 
being expressed in lumens. 

(14) The transmission ratio of a body 
for radiant energy of given spectral 
distribution is the ratio of the luminous 
flux passing through the body to the 
luminous flux incident thereat, both 
being expressed in lumens. 


We are informed that Engineer Vice- 
Admiral Sir George Goodwin, K.C.B., 
late Engineer-in-Chief of the Fleet, and 
Dr. James Colquhoun Irvine, C.B.E., 

F.R.S., Vice-Chancellor and Principal of 
St. Andrews University, have been 
a] "pointed by an Order of Council, dated 
August 10th, 1922, to be members of 
the Advisory Council to the Committee 
of the Privy Council for Scientific and 
Industrial Research. 



The Sixteenth Annual Convention of the Illuminating Engineering Society in the 
United States has been arranged to take place at Swampscott, Mass., during September 
25th 28th, 1922. An interesting programme appears to have been arranged, and 
the following tentative programme of papers and discussions is submitted: — ■ 

Tentative Program . 

Monday Afternoon. September 25$, 2.15 p.m. 
Address of Welcome, Dr. Thomson 

Presidential Address .. .. .. .. .. Dr. George S. Crampton 

Report of the Council by General Secretary .. .. Clarence L. Law 

Report of Committee on Progress .. .. .. F. E. Cady. Chairman 

Report of Committee on Nomenclature and Standards Dr. ( !layton ET. Sharp, .. 

Report of Committee on Education .. .. Prop. F. C. Caldwell, .. 

Report of Committee on Motor Vehicle Lighting Dr. Clayton II. Sharp, .. 

Tuesday Morning, September 26th, 9.15 ".//'. 

Residence Lighting Practice in the United States .. Norman I>. Macdonald 

A Survej of Residence Lighting.. .. .. .. .. M. Luceiesh 

Report of Committee to Prepare Bulletin on " Residence 

Lighting by Electricity" .. .. .. .. s. <;. Eibben, Chairman 

Reporl of Committee to Co-operate with Fixture Manu- 
facturers (a tentative outline) .. .. .. VI. Lucexesh, 

Sow to Tell Period Styles in Fixtures.. .. .. .. J. W. Gosling 

Tuesday Afternoon, September 2<i/A. 2.15 p.m. 

Performance of the Tungsten Filament Lamps on Alter- 
nating and Direct Current .. .. .. .. .. JOHN \Y. 1. 1KB 

Overcoming Daylight Reflections in Show 

Windows .. .. .. .. Ward Harrison and EL T. Spauuding 

Effect of Light <>n the Drawing Power of the Show 

Window.. .. .. .. .. .. \V. StURROCE and .1. M. Shite 

Lighting for Public Eating Places .. .. .. .. .. J. L. Stair 

Wednesday Morning, September 21th, 9.15 a.m. 
Lighting for the Food Industry.. .. .. .. .. W. H. Rademacher 

Practical Application of the Principles of School Lighting H. B. Dates 

Office Lighting from the Viewpoint of Hygiene .. .. A. B. Emmons 

The Cost of Daylighl .. .. ..' M. Luceiesh and L. L. Holladay 

Lighting for .Motion Picture Studios .. .. .. .. .. F. S. Mills 

Screen Brightness for Motion Pictures . . . . ('. F. EGELER and K. E. Farnham 

Wednesday Evening, September 27///. 

Symposium — A Fifteen- Year Advance in the Ait of Lighting — Presented by Authors 

of Papers given at the Society's First Convention at Boston. 1907. Comments 
on Present Practice. 

Messrs. Sharp, Millar. Marks. Bell, Ryan, Hale. Blood. .Morrison, Walker. &e. 

Thursday Morning. September 2&th, 9.15 a.m. 

A Direct Reading and Computing Attachment for Sphere Photometers B. S. Willis 
The Regular Icosahedron as a Substitute for the 

Dlbricht Sphere . . . . B. F. Shacelepord and K. S. Weaver 

A Distribution Photometer of New Design C. C. Colby and C. M. Doolittle 

Plotting of Spectrophotometry Curves . . . . . . . . F. A. Bexford 

Flicker Photometry — Parts I. and II. . . .. .. C. E. FERREE and G. RAN 

Thursday Afternoon, September 28th, 2.15 p.m. 
Measurement of the Fdectrical Response of the Betina 

to Stimulation by Light .. .. .. E. L. Chaffee and W. F. Bovie 

Report of Committee on sky Brightness .. .. H. H. Kimball. Chairman 

Lighthouse and Lightship Lighting .. .. .. .. . . S. G. Hibben 

Influence of Daylight Illumination Intensity on 

Electric Current Used for Lighting Purposes in 

the District of Columbus . . , . . . . . . . A. Smirnoff 




An instructive report was recently issued 
by Mr. Robert Davison, the Lighting 
Superintendent of the City of Newcastle- 
upon-Tyne, summarising the results of 
some improvements made in public 
lighting with gas. In 1920 the Depart- 
ment found that it was necessary to 
replace ] ,000 burners, owing to deprecia- 
tion during the war period, and this 
afforded an excellent opportunity of 
introducing a more up-to-date class of 
burner. Accordingly, in July, 1920, 
the adoption and fitting of superheated 
inverted burners in place of the existing 
upright ones was recommended. 

Inverted burners have many advan- 
tages over the upright type, such as 
the strong downward illumination, the 
cheapness in maintenance, and the fact 
that its application is less sensitive 
to conditions inherent in street lighting. 
In addition the use of a superheater 
leads to considerably greater efficiency, 
and the substitution of such burners 
in lanterns originally provided with 
upright types, is easily effected. In 
this case the work was carried out by 
the attendants in the course of their 
ordinary duties so that no additional 
expense for labour was incurred. 

It is remarked that good and efficient 
street lighting is an important asset 
to any town, and the efforts of the 
Lighting Department have accordingly 
been directed towards obtaining increased 
illumination combined with economy- 
It is stated that the improvement is 
obvious to a casual observer in the 
streets, and this is confirmed by photo- 
graphs taken under similar weather 
conditions. It would, however, have 
been instructive if exact figures for the 
illumination could have been furnished, 
showing the extent of the improvement 
in illumination, in the same complete 
manner as the economies derived. 

Renewal of mantles forms an important 
and expensive item in street lighting, 
owing to the variety of climatic conditions 
to which they are continually exposed. 
As is now generally recognised the 
upright mantle, having a much larger 
surface, and being only suspended from 
a clay rod by a thin asbestos loop, is 
easily destroyed by vibration, such as 

arises from stormy weather and heavy 
traffic conditions. The Bijou inverted 
mantle adopted is much stronger and 
smaller, and less easily affected. 

A tabulated statement is presented 
showing the great advantage secured 
in this respect. Thus, a No. 3 Kern 
upright burner requires on the average 
18T mantles per lamp per annum, 
whereas a 1 -light inverted needed only 
2*8 and a 2-light inverted burner only 
5 - 2 mantles per lamp per annum. The 
figures for 3-light and 5-light inverted 
were respectively 99 and 1L8 mantles 
per lamp per annum. It would seem, 
therefore, that on the average between 
two and three new inverted mantles 
have to be replaced during the year on 
each burner — a very much smaller 
number than was necessary with the 
upright types. The total number of 
burners used was the same in each case, 
but the expenditure on renewing inverted 
mantles was only £910 as compared 
with £3,633 for the upright ones — a 
saving of £2,723 during the year. This 
saving was doubtless effected mainly 
by the longer life of the inverted mantles, 
but it is also to be noted that the cost 
of the latter (53s. per gross) is substan- 
tially less than the cost of the upright 
(66s. to 116s. according to type). No 
doubt it is also an advantage to be 
using throughout inverted mantles of 
the same size. 

The increased efficiency of the inverted 
mantles has also enabled a considerable 
saving in consumption of gas to be made. 
The cost of gas for the upright burners 
was £27,024, for the inverted mantles 
£24,440 per annum, leading to a saving 
of £2,584. The total saving per annum, 
on mantles and gas consumed, is thus 
no less than £5,307 — a substantial amount 
saved by quite simple methods. 

As mentioned above, the report does 
not contain any actual figures with regard 
to the illumination produced. But it 
was stated in Mr. Sandeman's recent 
paper before the Illuminating Engineering 
Society that the inverted superheated 
burners use about 50 per cent, less gas 
for the same candlepower, so that the 
illumination now T afforded should be con- 
siderably higher than before the change. 




Some useful data on factors influencing 
the legibility of letter-signs were recently 
furnished by Mr. C. A. Atherton in the 
Electrical World.* The distance at which 
such a sign can be clearly distinguished 
depends on a variety of factors, including : 
(1) Dimensions of the letters, (2) Tip 
candlepower of lamp, (3) Colour of light, 
(4) Brightness of background and sur- 
roundings, (5) Size of the sign, (6) Atmo- 
spheric transparency, (7) Grouping and 
choice of letters, (8) Familiarity with the 
words, phrases or publicity pattern, and 
(9) Location of the sign. 

There is a theoretical maximum dis- 
tance of legibility. If details lie closer 
together than one minute of arc, their 
images strike the same unit of the retina, 
and they cannot be distinguished. Hence 
dimensions of letters are of fundamental 
importance. Candlepower of lamps may 
operate in various ways. Evidently, In 
order to be visible at night, souk- degree 
of brightness greater than surroundings 
is needed. But the eye has the quality 
of apparently increasing the size of 
brightly luminous objects ; as the person 
increases his distance the size of the 
filament appears to swell until it fills the 
bulb, and eventually may expand outside 
of it. Hence unduly bright lamps may 
actually diminish the legibility of a sign 
at a distance. The desirable brightness 
is also affected by atmospheric conditions. 
Dust, smoke and fog, which reduce 
atmospheric transparency, may, it is 
stated, have at first the effect of increas- 
ing distance of legibility. The absorp- 
tion of light may have an actual beneficial 
effect in diminishing the effect of irradia- 
tion. Colour is regarded as of relatively 
small importance from the practical 
standpoint, as distance of legibility is 
rot usually the most vital question 
whence colours are used for attractive 
effect. The presence of adjacent bright 
lights tends to limit the blurring of 
luminous spots. 

. The following formula is presented 
relating the various factors : — 



AB + 0-0083 D 

00035 D 

* Electrical World, May 27, 1922. 

Here S is the diameter in inches of the 
apparent spot of light measured in the 
plane of the light source, D is the dis- 
tance of the observer in feet, A is an 
inverse function of the tip candlepower 
of the light source, B depends on the 
light that enters the eye and the angular 
distance of each part of this light from 
the lamp. 

The following values of A, B, and AB 
are of interest : — 

Size of Park districts, Bright districts, 

lamp small signs large signs 

watts. 100 lamps. 200 1 lamps. 


10 34 3 102 20 680 

25 18 5 90 35 630 

50 14 5 70 35 490 

75 12 5 60 35 120 

100 10 5 50 35 350 

A useful diagram is presented connect- 
ing maximum legibility distance and 

h.eigh.1 of letter. It is interesting to note 
that the distance, for a letter of given 
si/.r. is somewhat greater with 10 watt 
lamps than with 75 lamps. Thus a 
letter-height of 25 inches gives 1,000 feet 
distance with 1<> watt lamps, about 750 
feet with 75 watt lamps. The relation is 
not far removed from a straight line, but 
the curve bends somewhat so that with 
the bigger letters the distance of legibility 
is somewhat greater than a straight fine 
law would suggest. Roughly, it would 
appear that the distance of legibility in 
feet is about 40 times the height of the 
letter in inches. This is less than the 
" theoretical maximum " referred to 
above, which, expressed in feet, is about 
70 times the height of letter in inches. 

Atmospheric conditions have, however, 
a great effect. In a somewhat denser 
atmosphere, lamps of higher candlepower 
are most effective, whereas in a clear 
atmosphere greater legibility is obtained 
with the lower candlepower. From the 
diagram it would appear that in general 
an advance from 10 watt to 75 watt 
lamps does not lead to an advantage 
corresponding with the greater consump- 
tion of energy and that lamps of small 
consumption are usually preferable. 




The photograph reproduced above was 
recently taken at the Croydon Aerodrome 
on the occasion of a demonstration by 
Major J. P. Ashley "Waller of a new type 
of projector which is being experimented 
with with the object of producing 
effective illumination of the landing area. 
The photograph was taken entirely by 
the light yielded by two of these new 
units, one of which is to be seen, mounted 
on a tripod, on the right of the photo- 
graph. The device utilises a 1,000 watt 
gasfilled lamp, equipped with a special 
dioptric lens, which serves to concentrate 

the light and produce a distribution 
favourable for the illumination of large 
horizontal areas. A striking effect is 
produced by the brightly illuminated 
faces of the buildings lining the aero- 

It will be recalled that the provision of 
a suitable ground illumination in aero- 
dromes was discussed on the occasion of 
the paper read by Lt.-Col. L. F. Blandy 
before the Illuminating Engineering 
Society in January last, and the experi- 
ments that are being made in this direc- 
tion will be watched with close attention. 


A note on the above subject in the 
" Transactions of the Illuminating En- 
gineering Society (U.S.A.) " for July 
remarks that, as the result of a collection 
of data in 32 cities with a combined 
population of over seven million people, 
it has been deduced that 17 6 per cent. 

of all deaths due to automobile accidents 
last year were caused by insufficient 
street illumination. It has been calcu- 
lated that the cost of these 567 deaths 
approximates in value to the total annual 
street-lighting bill of the United States. 
The position is thus similar to that of 
a man who is paying more for fire 
losses in his factory than he is for 




\Yi-: notice in Lirht uhd Lampe a short 
account of exhibits dealing with lighting 
at the Leipsic Fair. It is remarked that 
the present financial and economic situa- 
tion and the uncertainty felt as regards 
the future interfered with its success, 
especially as a sudden slump in the 
exchange made it difficult to fix prices. 

There were not many novelties in 
regard to lighting to record, but it was 
interesting to note in connection with 
silk shinies a general tendency towards 
natural and artificial silk fabrics in uni- 
form colour. Shades for table lamps in 
pagoda form, with decoration in Chinese 
style, were great favourites, and there were 
novel forms of portable lamps executed 
in ceramic material of various colours. 
There was also a fairly la rue output of 
fittings of the basketwork type. 

One point commented upon (that 
has also been noted in various English 
exhibitions) was the scattered nature 
of the exhibits on lighting, making it 

difficult to survey the section as a whole. 

It would l>e better for exhibits of this 
class to be assembled together. I Mi the 

other hand, this step presents difficulties, 
as many exhibitors have established a 

claim to a particular spot for their stalls 
and are reluctant to take new positions. 
The attendance from foreign countries 
is stated to have been good, especially in 
the more technical departments and in 
the hall devoted to the gas industry. 


Tenth Annual Meeting. 

It is announced that the Tenth Annual 
.Meeting of the Illuminating Engineering 
Society in Germany is to be held in 
Berlin on September 30th. 

Following the presentation of reports 
and usual business, a paper will be read 
by Prof. Dr. M. von Laue on " Our 
Present Conceptions of the Nature of 
Light."' Other contributions include : — 
" The Present Position and Future of 
Gas Lighting," by Dr. K. Bunte : 
" Impressions of Illuminating Engineering 

in the United States." by Dr. K. Finckh : 
and a demonstration of New Lamps 
Bur uii g Oi.s by E. AH- 


According to the Electrical World a 
new type of tungsten arc lamp has been 
developed by Phillips Glowlamp Works, 
of Eindhoven (Holland). The arc dis- 
charge takes place between two small 
tungsten spheres in an atmosphere of a 
rare gas. A third electrode midway 
I iet ween the feed wires is used to ensure 
striking the arc. A glow discharge sets 
in first between this third electrode and 
the adjacent one. thus starting the 
discharge between the tune-ten spheres. 

The distance between the spheres and 
the glass wall may be very small so that 
an optical condenser with a short focal 
length can be used when the lamp is 
applied for projection purposes. It is 
stated that the lamp can he run on a 
220 v. alternating circuit and except for 
; , series resistance no auxiliary apparatus 
is necessary. 


For some years there has been an 
impression that tin' term " fixture 
is not a happy one. It has no distinctive 
relation to illumination, and in many 
cases it is inappropriate. A tendency 
has recently developed, owing to the 
introduction of new wiring devices, 
to provide lighting fittings that are 
removable, that can, in short be hung 
in the same manner as a picture. To 
describe such a lighting device as a 
" removable fixture " is clearly a con- 
tradiction in terms. The Illuminating 
Engineering Society in the United States 
has, therefore, recommended the use 
of the term " luminaire " instead of 
fixture, a term that is already included 
in the French language and appears 
appropriate in English. 

It would be interesting to have the 
views of English experts on this proposal. 
It would probably be generally admitted 
that the term fixture, applying as it does 
to many objects that bear no relation to 
illumination, is not a very satisfactory 




By a Correspondent. 

Reference has recently been made in 
The Illuminating Engineer to various 
visits to countries where opportunities of 
developing illuminating engineering exist. 
Amongst those near at hand Norway 
should surely not be overlooked. A 
visitor is sure of a delightful holiday, and 
an illuminating engineer will find much to 
interest him in the methods of lighting 

Travelling in Norway, whether by rail- 
way or steamboat, is a pleasure. The 
usual course for English visitors is to 
travel by the Bergenske Dampskibsselskab 
Line from Newcastle to Bergen. The 
boats are comfortable and the lighting is 
fully up to the standard of modern vessels. 
In the dining room and lounge lamps in 
diffusing glass bowls are mounted direct 
on the ceiling : in the corridors lamps are 
placed between girders so that there is 
little impression of glare, and the cabins 
are also well illuminated. Vessels are 
equipped with wireless, and when ap- 
proaching Bergen the visitor is met by 
an offer of a free wireless message to that 
city engaging a cab. 

On reaching Bergen, in the evening one 
is at once aware that one has arrived in a 
new country. The rocky coast and islets 
and the unfamiliar buildings lining the 
quay, with the steep hills behind, present 
such a complete contrast to the passage 
down the Tyne ! In the evening the 
twinkling lights round the bay and the 
illuminated steamers form a charming 

The quay is well illuminated by gas- 
filled lamps in diffusing glass globes 
mounted on high masts, and there is also 
gas lighting. Norway, however, has 
practically no Coal of its own, so that gas 
is not often used. Electricity, on the 
other hand, almost invariably generated 
from water-power, is found everywhere. 
From a casual inspection of Bergen one 
forms the impression that the lighting as 
a whole is good. Most of the shop- 
windows utilise concealed methods or 

diffusing glass bowls, and there are some 
fittings, of a bell-like shape, which are 
not usually seen in England. In the 
Hotel Hospitsel, where the writer stayed, 
there is both gas and electric lighting. 
Here again one was struck by the 
general use of diffusing glassware and 
absence of glare, and the fittings, 
though of simple design, were distinctive. 
Other hotels visited during the trip 
were usually lighted by electricity, 
though in some remote spots oil lamps 
were used. At centres commonly visited 
by tourists the scheme of colouring was 
of a somewhat striking character, and it 
was observed that an attempt was made 
to design the lighting fittings to har- 
monise with the decorations. 

Most English visitors travel from 
Bergen on the Norwegian State Railway 
to Yoss, or some simila centre for 
tourists. The journey is an interesting- 
experience as the scenery gradually un- 
folds. The large windows in the special 
tourist cars afford a pleasing glimpse of 
wooded valleys and winding fiords. The 
latest types of carriages are lighted 
electrically, a novelty being the use of 
completely wired portable fittings for 
local lighting, which can be plugged into 
sockets at various convenient points in 
the compartment. 

This remarkable railway gradually 
rises from sea-level to a height of over 
4,000 feet near Finse, where the deep 
snow permits the use of " ski "* all the 
year round, afterwards descending to the 
fertile plains round Christiania. The 
scenery thus undergoes remarkable 
changes. A feature, which the writer 
believes to be unique among European 
railways, is that sleeping ears are provided 
not only in the first and second, but also 
in the third class. 

During the journey one gets a good 
impression of the characteristic features 
of Norway's valleys, with their scattered 
houses and occasional small industrial 
areas. It is a common sight to see over- 



head power lines coming down the slopes 
from some generating station in the hills, 
and to find local transformers on poles 
feeding some little cluster of houses. 
Factories are met with at unexpected 
points. Thus at the little town of 
Stanghelle there is one of the largest flour 
mills in the country : a little further 
along the line a large textile factory, with 
its attendant group of cottages for 
workers, has been erected. Electricity, 
derived from water-power, is almost in- 
variably used for lighting and power. 
Indeed, in some quite remote places large 
stations are being erected in the ex- 
pectation that industries will develop 
round them, as has been the case, for 
instance, at the Niagara Falls in America. 
From Voss the traveller will probably 
proceed by motor car to Stallheim, with 
its sensational ravine descending to the 
fiord at Gudvangen. At this quiet little 
spot the sun is never seen for three 
months in the winter, being always 
blocked by the adjacent steep hills. 
Gudvangen gives access to the Sognefiord 
with its innumerable beauty spots. The 
scenery of the fiords of Norway has often 
been described but must be seen to be 
appreciated. The view in some of the 
narrow fiords is apt to be sombre, and 
bright sunshine is needed to bring out 
the colours and display them at their 
best. The tourist soon discovers that 
his movements are largely dictated by 
the times of arrival and departure of 
these little fiord-steamers. If, as once 
happened to the writer, he arrives at 
11 p.m., he may wonder why the ubi- 
quitous electricity is not applied to light 
the quay. The absence of public lighting 
is partially remedied by the steamboats 
which utilise hooded fittings equipped 
with a bunch of electric lamps, a species 
of flood-light, to facilitate the landing of 
passengers and cargo. But, once landed, 
the passenger may have to proceed to 
his hotel in impenetrable darkness. True, 
most of the places of call for steamers 
are small, and the inhabitants doubtless 
retire early and have little need of public 
lighting. But, for the benefit of visitors 
the plentiful supply of electricity might 
well be applied to illuminating landing 
place and lighting up the name of the 
place, as is customary on modern railway 

Pleasure steamers usually proceed 
fairly directly to their destination, but 
others visit so many places and have so 
much cargo to unload, that the journey 
is somewhat dilatory. Visitors to Skjol- 
den. for instance would do well to break 
the journey at the Hofslund Hotel at 
Sogndal, whence they may take a delight- 
ful motor trip towards Turtegro, the 
centre for the famous Skagastoldstinderne 
mountains. Alternatively they may pro- 
ceed to the great Jostedaal glaciers, at 
the very foot of which a new hotel has 
recently been erected. 

The largest glaciers in Europe descend 
to the foot of the fiord at Fjaerland, a 
most delightful little spot, from which 
many fine excursions may be made. The 
view up the glacier, terminating in the 
tumbled mass of ice at the summit, with 
its strange blue colouration in certain 
lights, is most impressive. 

There is equally novel and interesting 
mountainous scenery on the other fiords 
of Norway, and the Jotunheim contains 
grand walking country which is taken 
full advantage of by Norwegians but is 
rarely visited by English people. 

Visitors to Norway cannot fail to be 
struck by the general resemblance of the 
people to the British, and by the freedom 
with which English is spoken throughout 
the main tourist routes. But if they 
go further afield they will have little 
trouble and will find proprietors of hotels 
friendly and obliging. English visitors 
are made welcome, and travelling is 
simple. Matters are settled in a free 
and easy manner with a minimum of 
red tape. 

In conclusion the writer would like to 
take this opportunity of acknowledging 
the courtesy and assistance he received 
from Bennett's Travel Bureau, who have 
made a speciality of Norway for many 
years ; the Bureau has an office in Loi don 
which intending visiters should consult. 
The somewhat complicated tour taken by 
the writer was planned out by them in an 
admirable manner, and with an apparent 
insight into psychological effect — a fea- 
ture being the ascending merit of the 
scenery as one advanced, so that each 
day brought something fresh and the 
interest was maintained to the last. 

J. S. D. 




— « • • • • — 

[At the request of many of our readers we have extended the space devoted to 
this Section, and are open to receive for publication particulars of interesting 
installations, new developments in lamps, fixtures, and all kinds of apparatus connected 
with illumination. 

The contents of these pages, in which is included information supplied by the 
makers, will, it is hoped, serve as a guide to recent commercial developments, and we 
welcome the receipt of all bona-fide information relating thereto.] 


The possibilities of modern gas lighting 
for shop-lighting are admirably illustrated 
in a recent issue of " A Thousand and One 
Uses for Gas," in which attention is 
drawn to the value of good illumination of 
windows as a sound advertisement. 
Many of the leading shopkeepers, it is 
remarked, now leave their windows fully 
lighted up to a late hour every evening, 
and by means of clockwork controlled 
taps lights can be extinguished at any pre- 
determined time. 

Windows are commonly illuminated by 
lights situated above the display at the 
top, in the manner indicated in the illus- 
tration on p. 236. It is essential that 
such lights should not be exposed to the 
eyes of people looking into the window, 
and the provision of some form of frieze 
carrying advertisements, as in this case, 
offers a convenient mode of screening the 
mantles. Another method, now in favour 
in many districts, is the use of outside 
lamps, which . can be controlled from 
inside the shop by means of special cocks. 
The second illustration (p. 237) shows 
the use of this form of lighting, a feature 
being the use of parabolic reflectors to 
conceal the lamps from view and direct 
light on to the goods. 

While the advertising value of good 

outside lighting during the dark hours of 
the evening cannot be disputed, the shop- 
keeper naturally desires to keep the cost 
as low as possible. Attention is therefore 
drawn to the advantages of the new super- 
heated inverted incandescent burners, 
which give on the average 50 per cent, 
more light per cubic foot of gas burned 
than the ordinary low-pressure inverted 
incandescent burner. The chief features 
of this type of " cluster " lamp are : — 

(1) The provision of a superheater 
through which the gas and aii mixture 
passes to the burners in a preheated con- 

(2) The employment of small gas 
mantles in a " cluster " form. 

(3) The use of a single gas and air 
regulator to adjust, by one turn, the whole 
of the burners. 

In shopping areas, where there is no 
high pressure main, these cluster lights 
should be employed. 

For the two illustrations, referred to 
above, we are indebted to the courtesy 
of the British Commercial Gas Associa- 
tion. This association and gas under- 
takings are always pleased to place then- 
experience and expert advice at the 
disposal of consumers, who would also 
be well advised to arrange for maintenance 
by the local gas concern. 



A good arrangement for lighting a confectioner's. The lamps are mounted well above 
the contents of the window, and are screened by the diffusing glass panels. Most 
of the light is directed downwards, but some of it is allowed to illuminate the 
lettering on the panels above the window. 



This photograph illustrates the effective use of outside lamps, the mantles being screened 
from the view of persons on the pavement and their light directed on the goods. 
Such lamps can now be completely controlled from the inside of the shop by 
means of a special cock. 



In a recent issue we referred to the 
<lin-(-t ive system of street Lighting devised 
by Mr. Haydn T. Harrison, describing the 
u><- of two inclined minors Immediately 
adjacent to the Lamp, in order to modify 
the natural curve of light distribution. 
We should Like to mention that the action 
of these mirrors is dependent on the use 
of a special concentrated reflector above 
the tamp. The rays thus concentrated 

are received by the mirror, and directed 

tot he distant part of t lie street. 

A diagram shows that at these distant 
parts the candlepower is increased to 
nearly ten times that of the source, but 
thai it rapidly decreases to the normal 

power of the source a- SOOD OS the light 
is approached. 'Inns the more powerful 

rays are only visible at a considerable 
distance, a condition which helps feo 
diminish liability of glare, besides pro- 
moting even illumination. 

From a diagram illustrating the effect 

■ I 300 watt units spaced at a distance of 

150 feet, it is shown that whereas the 
illumination under the Lamps is approxi- 
mately 1 foot-candle, that midway be- 
tween them is as much as 0'25 foot- 

candle, i.e., the diversity factor is only 
1 : 1. a very moderate figure in view of 
the wide variations in illumination com- 
monly met with even in streets considered 

well lighted. 


We notice that Oral Topics, a journal 
which deals with dental hygiene, for July, 

contains an article by Dr. Adrian Klein. 

explaining the applications of the Shering- 
ham Daylight, which appears to have 
beerl found especially useful to dentists. 
Advertisements in this issue include one 
by the Midland Dental Manufacturing 
Co., Ltd., who state that they employ this 
Lighting unit to facilitate the selection of 
artificial teeth. Importance is attached 
to the careful selection according to colour 
of artificial teeth, and the use of artificial 
daylight has proved of great service in 
facilitating accurate matching. 


We are informed that Messrs. The 
English Electric & Siemens Supplies, 
Ltd., have received a contract for the 
supply of Siemens Britannia Metal Fila- 
ment Lamps for six months to the Booth 
Steamship Company. Also that a tender 
has been accepted by the Great Northern 
Railway Company for the supply of 
Siemens Britannia lamps for t rain lighting. 


A booklet issued by Messrs. W. T. 
Henley & Co. contains a description of 
the Henley Wiring System, a feature of 
which is the ease and speed by which it 
can be installed at a moderate c 

The wiring system has been recom- 
mended in connection with housing 
-(■heme,, and is stated to have been very 
successfully and expeditiously used at 
Bradford and elsewhere. 

It is not generally known, however, 
that the system, which complies with the 
rules of the Fire Insurance Offices, and 
the wiring rules of the Institution of 
Electric Engineers, has also been used in 
many larL. r >' building- of distinction. 

The pamphlet before US contains illus- 
tration- of a large number of country 
house- where the system has been in- 
stalled, a- well a- in connection with 

village lighting and Government housing 

scheme-, churches, cathedrals and public 

buildings, including some in the Colonies 

and Dominions. 


A catalogue of lighting fittings, issued 
by Messrs. A. W. Beuttell, Ltd. (53, 
Victoria street, S.W.), contains particulars 
of the Linolite-Tubolite Fittings for shop 

lighting and other shop-window fixture-. 

enabling the light to be concentrated on 
the goods. The Sunburst fixture is a 
novel device that deserves attention. 

This consists of an artificial skylight, i.e.. 
an arrangement of lamps above panels of 
diffusing glas-, to simulate a window in 
the ceiling. 

The well-known Beuttell system of 
illuminated signs is also illustrated. 


Our attention has been drawn to an 
interesting development in lamp-shades, 
namely, their impregnation with a sub- 
stance that is claimed to render them 
non-inflammable, more translucent, wash- 
able and dust-proof. 

A sample of silk fabric so treated, sent 
us by Messrs. Charles Selz, affords an 
interesting contrast to untreated material. 
The impregnated surface appears darker 
by reflected light, but considerably 
brighter by transmitted light, and has a 
taut shiny surface less liable to collect 
dust. It is also stated that it will with- 
stand repeated washing and rough treat- 





An invitation was recently extended 
to members of the Circle of Scientific, 
Technical and Trade Journalists and 
representatives of the technical press, 
to visit the new showrooms and labora- 
tories of Holophane Ltd. at Elverton 
Street, Westminster. 

The party was received by Mr. H. H. 
Thompson (managing director), and an 
address was afterwards given in the 
showroom by Capt. E. Stroud. The 
showroom is decorated in a novel 
manner, using chiefly black walls bearing 
a gold design, and an upper white frieze 
and ceiling. In addition to pendant 
fittings it contains a section having a 
species of stage on which typical glass- 
ware of all kinds may be mounted, and 
which also permits the use of a small 
screen and lantern for lecture purpose^. 

In his opening remarks Capt. Stroud 
recalled that the development of scien- 
tific globes and reflectors had naturally 
followed the introduction of electric 
light. Prior to this period the cnly 
illuminants available (candles, oil lamps 
and flat -flame pas burners) were of com- 
paratively small brilliancy. But the 
much greater brightness of the filaments 
of electric lamps demanded shading, a 
need that was further emphasised when 
the brighter metal filaments and gas- 
filled lamps arrived. 

At the same time it came to be appre- 
ciated that distribution of light was also 
of importance. The Holophane glassware 
was accordingly designed to effect both 
objects, to screen the source of light and 
to direct the rays in directions where 
they were chiefly needed. Early Holo- 
phane designs involved the use of two 
kinds of prisms, internal and external. 
A distinct advance was the introduction 
of reflectors with a smooth interior and 
external prisms whereby a great range 
of variation of light distribution was 
made possible. Many special units had 
been evolved for use in streets, shops, 
churches, factories, etc., and some of 
these were exhibited and described. 

Attention was drawn to the new '"arti- 
ficial daylight " units, the effect of 
which was demonstrated in the laboratory 
to the Holophane motor-headlight and 
the new " flood-lighting " unit. The 
lecturer emphasised the fact that the 
company, early in its career, had accepted 
the principle of rendering service, by 
showing consumers how to use lighting 
units as well as supplying them. It had 
consistently aimed at keeping abreast of 
progress, as exemplified by discussions be- 
fore the Illuminating Engineering Society. 

In making a tour of the premises 
visitors were impressed by the extensive 
warehouse for the storage of glassware 
and by the well-equipped laboratory in 
which polar curves of light distribution 
can be worked out and Holophane 
Lumeters tested. 

Mr. Leon Gaster, Chairman of the 
Circle, in returning thanks for the invita- 
tion, expressed the hope that in future 
each development in applied science 
would be brought before the technical 
press, which acted as an educational 
link between the expert and the general 
public. Lighting was literally of interest 
to everyone. The importance now at- 
tached to the subject was illustrated by 
the appointment, in 1913, of the Home 
Office Committee on Lighting in Factories 
and Workshops, of which he was a mem- 
ber. Successful lighting was necessarily 
based on the consideration of the im- 
pression received by the eye. " Light on 
the object not in the e$e " was a prin- 
ciple that should always be observed. 
Mr. Gaster added that an installation. 
besides being carefully schemed out 
initially, required systematic main- 
tenance. In particular it was necessary, 
in replacing lamps, to use only types for 
which reflectors were suited. The light- 
ing unit, comprising the lamp and its 
appropriate globe, bowl or reflector, 
should be treated as a distinct entity, 
and co-operation between lamp makers 
and manufacturers of glassware was of 
threat importance. 




The " Ceag " Pillarless Lamp has been 
introduced with a view to increasing the 
amount and distribution of light given by 
miners' electric lamps, and lias bees ap- 
proved by the Home Office for use under- 
ground, after exhaustive tests in mines 
over a period of two years. 

The lamp consists of a standard miners' 
lamp, fitted with a special reflector carried 
by a bridle, capable of swivelling in a 
larger bridle from two points at the Bide 
of the lamp top. The large bridle is 
secured by heavy screwed pins entering 
strengthening lugs riveted to the lamp 
top. The remaining portion of the lamp 
is built up of standard parts, inter- 
changeable with the existing standard 
" ( leag " Miners' Lamp. 

The advantages claimed for the pillar- 
less lamp are as follows : with the re- 
flector down an increase of light of 70 per 
cent, is obtained. There are no dark 
shadows caused by the lamp pillar-, a 
clear beam of light over an arc of 160° is 
thrown forward. The reflector can, if 
necessary, be placed completely over the 
well-glass of the lamp. 

The improved distribution of light is 
strikingly illustrated in a diagram com- 
paring the standard and pillarless lamps, 
a maximum candlepower of nearly 2*6 BE 
compared with To being shown. 

The "Ceag" Pillarless Miners' Lamp. 


A catalogue recently received from the 
Allen-Liversidge, Ltd., illustrates one 
special quality of acetylene lighting, 
namely, the ease with which candles can 
be imitated. It will probably be ad- 
mitted that the electric candle is not 
usually a very close imitation of the 
natural article, as it is difficult to design 
filaments which resemble a flame. With 
acetylene, however, one can obtain a 
flame similar in shape to that of a wax 
candle. This point is interesting, because 
there are certain traditional types of 
fixtures which demand the use of candles. 
With acetylene, however, the anomaly of 
introducing a new illuminant in a chande- 
lier originally designed for use with wax 
candles is less evident. 

The accompanying illustration shows a 
typical candle-bracket of pleasing design. 


INDEX, August, 1922. 


Aerodrome, Night Lighting of a 

Editorial. By L. Gaster 

Illuminating Engineering Society (U.S.A.), Forthcoming Convention 

Illuminated Signs, Legibility of 

National Illumination Committee, Chairman's Report and List of Definitions 
and Units 

Newcastle-upon-Tyne, Gas Lighting Developments in 

Norway, Some Impressions of 

Reviews of Books 

Topical and Industrial Section : — 

Shop Lighting with Gas — Directive Street Lighting — Modern Electric 
Wiring — Artificial Daylight for Dentists — New Holophane Show- 
room and Laboratories — A Novel Illuminated Sign, etc. 






Telephone Troubles and How to Find Them. 
By W. H. Hyde. (S. Rentell & Co., 
London. 9dt net. pp. 56. 35 diagrams.) 

This little book has now reached its nine- 
teenth edition, and is available at a 
moderate price. Particulars of magneto 
and common battery systems are given 
and line, cable, instrument and switch- 
board troubles are discussed. A list of 
professional papers dealing with subjects 
of interest to telephone and telegraph 
engineers and procurable from the pub- 
lishers, is included at the end of the work. 
The information is condensed and fully 
illustrated, and the book should continue 
to be useful to those concerned with 
telephone work. 

Converting a Business into a Private 
Company. By Herbert W. Jordan. 
(Jordan & So)is, Ltd., London. 1922. 
pp. 48.) 

This work attempts to explain in simple 
terms the procedure necessary in con- 
verting a business into a private company. 
A hypothetical case is discussed and the 
preparation of the memorandum of 
association and other documents is con- 
sidered. At the end is a summary of 
duties and fees payable on incorporation 
of companies having a share capital. 

Practical Optics for the Laboratory and 
Workshop is the title of a book by Mr. 
B. K. Johnson, late of .Messrs. A. Hilger, 
Ltd., Lecturer in Optics at the Imperial 
College of Science and Technology, which 
Messrs. Benn Brothers will publish this 
autumn. Professor F. J. Cheshire, F.R.S.. 
Director of the Optical Engineering De- 
partment, Imperial College of Science and 
Technology, contributes a foreword. 

We are informed that the work recently 
issued on Elementary Determinants for 
Electrical Engineers, by H. P. Few. and 
the new (2nd) edition of Electric Bells, 
Alarms aiui Signalling Systems, by H. G. 
White, both published by S. Rentell & 
Co., Ltd., have been included in the works 
of reference recommended by the ex- 
aminers of the City and Guilds of London 

Messrs. Wallis- Jones & Dent, Consulting 
Engineers (Reginald J. Wallis-Jones, 
O.B.E., M.Inst. C.E., M.I.E.E.), have re- 
moved their office from 23, Old Queen 
Street, S.W.I, to 50, Queen Anne's Gate, 
Westminster, S.W.I (i.e., their pre-war 
address); Telephone: 8070 Victoria. 





A remarkable advertising sign 
has just been erected on the Mazda 
Electric Lamp Factory at Rugby. 
This sijm stated t<> be the biggest, 
heaviest, and most brilliant of 
its kind in the Kingdom— over- 
looks tin- London and North- 
Western mam line and is seen 
every day by thousands of 
passengers. It measures 33 feel 
by 22 Eeet, and consists of opal 
glass-faced Letters on a steel frame- 
work, bolted to th.' factory roof. 
Instead of being lighted by a 
number of small Lamps fixed t«. 

the sign itself, it is illuminated far 
more brilliantly and effectively 
from a distance by means of 
B.T.-H floodlight projectors 
equipped with .Mazda Gasfilled 
lamps. By the former method, at 
least eight hundred K) watt lamps, repre- 
senting a total consumption of 8,000 

watts, would have been required. By the 

11( . w method a much better effect is 
obtained from four 1,000-watt Mazda 

Gasfilled lamps. The method has the 

further advantage of eliminating glare, and 

the message stands out in letters of fire 
againsl the inky background of the nighl 
sky. The individual letters alone are 
Lighted, and these are sharply defined 
against the. surrounding blackness. All 
else is invisible. In effect, the new 
method represents the application of the 
naval searchlight to the needs of out- 
door publicity. 

Full information in regard to the 
B.T.-H. system of sign-lighting may be 
obtained from the Illuminating Engineers' 

view of sign. The "M " of .Mazda is II feet 
high. The letters are opal-faced. 

Department of the British Thomson- 
Houston Company, Ltd., Rugby, and 
77, Upper Thames Street, London, E.( '. 1. 
The construction and erection of the 
sign itself were carried out by J. Akers. 
of Medina Works, Kew Green. 

Barimar, Ltd., 10, Poland Street, 
Oxford Street, London, W.l, and Branches, 
have issued a comprehensive booklet 
which includes almost every kind of 
engineering repair work. Those of our 
readers who are interested should write 
for a copy of the booklet. 

A recent leaflet issued by the London 
Electric Firm (Croydon) illustrates the 
use of the suspension system of street 
lighting at Hove. We understand that 
the method has been installed in many 
other cities. 



^Humiliating Engineering Society. 

(Pounded in London, 1909.) 


Tel. No. Victoria 5215. 


Progress in Illuminating Engineering. 

One of the chief items in the proceedings at the Annual Convention 
of the Illuminating Engineering Society in the United States is the 
presentation of the " Report of Progress " which has now been published 
in the Society's Transactions for September. The scope of the Report 
has been continually extended, and it now contains an admirable survey 
of developments, not only in the United States, but in Europe. 

As regards illuminants, while there are no very striking novelties 
to record there have been many instances of steady progress in detail. 
Perhaps the most interesting step from the scientific standpoint is the 
introduction of the new small voltage neon lamps, particulars of which 
have already appeared in this Journal. It is interesting to observe that 
the proportion of carbon filament lamps produced in the U.S.A., continues 
to diminish ; ' such lamps now form only 3'6 per cent, of the total output. 
Another notable development is the growing tendency towards standardisa- 
tion of voltage (no, 115 and 120 volts). The proportion of lamps made 
for this range of pressure has now risen from 76 to 92 5 per cent., and this 
naturally makes it easier for manufacturers to produce better and cheaper 
lamps. A new country to embark on electric lamp manufacture is Finland, 
where a factory capable of producing 300-400 lamps per day is said to have 
been started. 


Many lighting installations of a novel character are mentioned. The 
account of new street-lighting installations affords striking evidence of 
the enterprise of American cities where the benefits of good public lighting 
seem to be fully realised and where, apparently, the need for economy 
is not felt so severely as has recently been the case in this country. The 
use of flood-lighting in pageants has been a feature. A novel development 
of this method of lighting has been to illuminate the smoke from a factory 
chimney, so as to afford a guide to the conditions of processes carried on. 
Industrial lighting also receives a large share of attention and the reports 
of the Home Office Committee on Lighting in Factories and Workshops 
in this country are mentioned. The standard of illumination in the United 
States seems to be progressively rising and further instances of increases 
in output, fully justifying the installation of better lighting, are mentioned. 
Thus in one works, where the cost of the improved lighting formed only 
o - o66 per cent, of the cost of production, the output was increased by 
8' 5 per cent. 

Luminous signalling devices seem to be playing an important role 
in the regulation of traffic. The Liverpool elevated railway is mentioned 
as an instance of the successful use of coloured-light railway signals in the 
daytime and the method lias been the subject of study by the British 
Ministry of Transport. The Committee on Standards of the American 
Association of State Highway Officials has obtained endorsement of over 
200 cities and a large number of automobile clubs and associations that 
red, yellow and green should be used in road traffic to indicate respectively 
" All traffic stop," " Proceed with caution " and " Road intersection 
dangers." There has also been progress in the design of lighthouses and 
beacons, a notable development being the installation of an aerial lighthouse 
stated to produce a beam of 1,000 million (maximum) candlepower, near 
Dijon, in France. A general improvement in the design of " luminaires " 
(lighting fittings) in the United States is recorded, and steps are being 
taken to promote fuller co-operation between makers of fittings and 
manufacturers of electric lamps. 

In the section of photometry interest attaches to recent work on 
photo-electric cells which may presently lead to useful practical applications. 
The miscellaneous applications of light and problems mentioned in the 
latter part of the report also make fascinating reading. Some of these 
researches relate to the phosphorescence of insects and marine organisms, 
others to the effect of light on the eyes of various creatures. Equally 
interesting are the experiments being conducted on the influence of light 
on plant growth, a problem that deserves closer study by agriculturists. 
In view of the attention recently devoted in this country to the problem 
of avoiding troublesome reflections off the shiny surface of pictures, the 
use of polarising apparatus to eliminate such effects deserves mention. 
The device has been applied to the expert study of " old masters," and is 
also said to have proved useful in various physiological researches. 

In the final section on Legislation it is mentioned that the State of 
Massachusetts has issued a tentative code on industrial lighting, and that 
a similar code is being considered by the State of Washington. It is stated 
that the Department of Education of New York City has started a course 
in the Principles of Artificial Lighting — a step that deserves attention 
from educational authorities in this country. i\t the end of the Report 
there is a list of recent works on lighting and illumination, including several 
recently issued in this country. 


Popular Demonstrations of Lighting. 

At this season of the year it is usual for gas and electric supply com- 
panies to arrange for public demonstrations of lighting appliances. Some 
companies have shown enterprise in this direction, but there are others 
who do not as yet do as much in this direction as is desirable, while the 
occasional displays arranged by firms concerned with lamps and lighting 
fittings not infrequently receive insufficient notice. Such exhibits some- 
times fail in their object because the public are merely shown lamps such 
as may be seen any day in a showroom, and do not devote sufficient attention 
to their application in the form of illumination. In order to arrest public 
attention something novel and attractive must be shown. Above all 
members of the public must feel that the display has a personal application — ■ 
that they are seeing devices and matters which they can readily apply 
in their own homes. 

The Model Bungalow, completely equipped and lighted by gas by 
the Croydon Gas Company, an account of which is included in this issue 
(pp. 262-263), is an interesting attempt in the right direction. The display 
was well-patronised, and in many of the rooms the combined effect of the 
lighting and the system of decoration was charming. A good feature was 
the general use of vitreosil glassware to screen the mantles, usually supple- 
mented by silk shades of pleasing design. We are glad to see that the 
fundamental principle of avoiding glare, emphasised in Mr. Sandeman's 
recent paper before the Illuminating Engineering Society, was adhered 
to throughout. 

Properly organised shows of this kind should bring a direct return 
to the company concerned. But too much importance should not be 
attached to immediate sales. Such displays are essentially educational. 
Their influence is cumulative and the benefits are often spread over a 
considerable period of time. The chief aim should be to bring home to 
the consumer the conviction that the Company is interested in his needs 
and is anxious to help him, that it has behind it useful scientific information, 
and can tell him something that he does not know already. The display 
should be supplemented by informal addresses and conferences on lighting, 
but in order to make a success of this feature there must be available experts 
who are familiar with the latest developments in illuminating engineering, 
and who can answer questions and show themselves to be masters of their 

If the display is conducted on these lines a company is justified in 
aiming at much wider publicity than if it is merely " out to sell " and the 
co-operation of the technical Press may be invited. An instance of 
successful co-operation of this kind was afforded by the recent demonstration 
at the new showrooms and laboratory of Holophane, Ltd., noticed in our 
last issue. In all such cases the aim should be to illustrate successful 
applications of light. Lantern slides of photographs, taken by the artificial 
light provided, are useful. Another step that might sometimes be arranged 
would be to invite experts on lighting and members of the technical Press 
to visit actual installations of outstanding interest, particularly well- 
lighted factories with the double object of examining the method of lighting 
and seeing the industrial processes carried on. This step would, naturally, 
involve the co-operation of the firm whose premises have been lighted 
but in many cases they would doubtless welcome such a suggestion. 


The Use of Artificial llluminants in Kinema Studios. 

A few months ago we mentioned that we had received an important 
report of researches on the above subject conducted in the laboratory 
of the Eastman Kodak Company, the first instalment of which now appears 
in our present issue. The treatment of the subject falls naturally into 
two divisions : (a) The study of the characteristics of photographic materials 
and their response to different forms of radiation ; and (b) the effect of 
light and radiation on the human eye. 

As a basis for a complete investigation of this kind the choice of terms 
and definitions, both photometric and photographic, needs special care. 
The former follow well-established lines, but some of the photographic 
terms have to be specially defined for the present purpose. Some examples 
are given illustrating the difference in distribution of energy, luminosity 
and photographic effect in the spectra of llluminants and the method of 
judging photographic efficiency, in terms of the density of the image produced 
by a given illumination and the " inertia " of the plate is explained. This 
method is of considerable consequence, as in the past some misconceptions 
have arisen owing to the conditions of test not being clearly indicated. 
In particular it is to be noted that the relative photographic efficiency 
of Llluminants depends greatly on the nature of the photographic plate 
or film for which they are used. The author accordingly draws a distinction 
between ordinary orthochromatic and panchromatic materials, and it will 
be observed that the llluminants which are apparently most efficient for 
the ordinary plate (chiefly sensitive to blue light), are not necessarily the 
best for materials with a wider sensitiveness to colours throughout the 

Another point that needs to be made clear is whether the illuminant 
is judged on the basis of the time of exposure needed to produce a certain 
density with a given illumination, or for a given expenditure of energy. 
Tables worked out on both these principles are presented, and another 
interesting series of tests shows how the photographic efficiency of a gas- 
filled tungsten lamp is increased with rising voltage. It is suggested that 
in some cases it may be expedient to operate lamps at a voltage higher 
than that normally used— a point that deserves attention from artists 
in portraiture studios, where gasfilled lamps are commonly employed. 

Finally, reference is made to some interesting tests on types of flame 
carbons used with colour-filters, such as are commonly used in taking 
colour-films and in photo-engraving. The fact that marked variations 
in quality of light may be produced by altering the constituents in the 
cores of flame carbons is worth consideration in work of this kind. 

The present section of the report thus enables us to estimate the effect 
of various illuminants in photographic work. In order to relate completely 
intensity of illumination and exposure it is also necessary to take into 
account the absorption of light in the lens system, etc., and the next section 
of this contribution will show how this may also be done. 

There are, doubtless, opportunities for much valuable research in the 
use of artificial illuminants, both in portraiture and kinema studios, and 
it will be recalled that a special committee of the Illuminating Engineering 
Society was formed last year to deal with this matter. Experiments in 
this field of work should receive every encouragement. 

Leon Gaster. 

THE 1LLI"ML\.\TIX<; ENGINEER (sept. 1922) 



By Lovi) A. Jones. 

A complete study of the lighting of 
kinema studios involves a consideration 
of many factors and a knowledge of 
photometry, and visual and photographic 
sensitometry. Of the information neces- 
sary for the proper use of artificial 
illumination in kinema studios much is 
not generally known and its application 
to practical problems imperfectly under- 
stood. Hence it seems worth while to 
review all aspects of the subject, sum- 
marising present knowledge and indicat- 
ing opportunities for further experiment. 

The treatment falls naturally into two 
main divisions : — (1) The study of the 
characteristics of photographic materials 
and their response to different forms of 
radiation ; (2) the consideration of the 
human eye, its characteristics and the 
possibilities of injury due to excessive 
intensity or the special quality of the 
radiation emitted by the sources used. 

Two sources of equal visual intensity 
may differ widely in their action on a 
photographic plate, which is sensitive to 
a region of the spectrum quite distinct 
from that producing the sensation of 
light. The maximum visual sensation 
occurs approximately at 550 /i/x, whereas 
the maximum response of the photo- 
graphic plate is located near 440-460 /x/n. 
Hence if the eye is used as the basis of 
judgment of adequacy of illumination in 
a kinema studio, errors may arise. 
The rendering of tone-values by photo- 
graphic material may be quite different 
from that suggested by the visual appear- 
ance of the objects illuminated. A 
knowledge of the relative visual and 
photographic efficiencies of illuminants 
used is, therefore, of importance. 

The first part of this paper will be 
devoted to the study of the effect of 
radiation on photographic materials, the 
second part to possibilities of injury to 
the eyes of workers in kinema studios, 
either through radiation of harmful 
quality or excessive intensity. 

Terminology, Nomenclature and 

A logical system of terminology is 
essential to the complete study of this 
subject, otherwise confusion will in- 
evitably result. An approved system of 
terms and units used in photometry has 
been developed by the Committee on 
Nomenclature and Standards of the 
Illuminating Engineering Society (U.S.A.) 
and will be adhered to in what follows. 
But the nomenclature of photography 
has been less completely developed. In 
dealing simultaneously with photometry 
and photography one must depart some- 
what from common usage in order to 
avoid confusion of terms. It is hoped 
that the proposals for some new photo- 
graphic units will be of service. 

Photometric Terms. 

(1) Light is used to denote the visual 
sensation produced when radiant energy 
within the proper limits of wavelength, 
and of sufficient intensity and duration, 
impinges on the retina. 

(2) Radiant Flux (J). The rate of flow 
of radiation evaluated with reference to 
energy, expressed in ergs per sec. or 

(3) Luminous Flux (F). The rate of 
flow of radiation evaluated with reference 
to visual sensation, expressed in lumens. 
The lumen (1) is the unit of luminous 
flux and is equal to the flux emitted in 
unit solid angle (steradian) by a point 
source of unit luminous intensity. 

(4) Visibility (V) of radiation of a 
particular wavelength is the ratio of the 
luminous flux at that wavelength to the 
corresponding radiant flux. 

(5) Luminosity (L) of a particular wave- 
length is the product of the visibility and 
the corresponding ordinate of the spectral 
curve of radiant flux. It is represented 
by the ordinate of the spectral curve of 
luminous flux, and the curve derived 

* Communication No. 135 from the Research Laboratory of the Eastman Kodak Co. ; 
slightly abbreviated. 



from such ordinate* is the " spectral 
luminosity curve " which varies for 
different sources. 

(6) Luminous Intensity (1) is the 
luminous flux per unit solid angle emitted 
by the source in the direction considered. 
The unit of luminous intensity, the 
<<n <i/h\ is maintained by the national 
laboratories of France, Great Britain and 
the United States. " Candlefower " (c.p.) 
is luminous intensity expressed in candles. 

(7) Illumination (N) of a surface at 
any point is the luminous flux density at 
that point (flux per unit of area illumin- 
ated). The lux (metre-candle) is equal 
to one lumen per square metre. The 
fool-candle {i.e.) is equal to one lumen per 
square foot. 

(8) Brightness (B) may be expressed in 
terms of luminous intensity per unit of 
projected area of the surface, or in terms 
of the flux | iroc. mm ling from one unit area 
of the surface. The lambert is the bright- 
ness of a perfectly diffusing surface 
emitting or reflecting one lumen per 
sq. cm. For most purposes the milU- 
lambert (ml.) is the preferable practica 

(9) Luminous Efficiency (C) of a source 
is the ratio of luminous flux to the radiant 
flux emitted and is expressed in lumens 
per watt. 

(10) The Mechanical Equivalent of 
Light is the ratio of radiant flux to 
luminous flux for the wavelength of 
maximum visibility and is expressed in 
watts per lumen. 

(11) Reflection Factor (R) is the ratio 
of the flux reflected to the incident flux. 
In practice there is usually a mixture of 
regular and diffused reflection. 

(12) Absorption Factor (Ab) is the 
ratio of flux absorbed by the body to 
the incident flux. 

(13) Transmission Factor (T) is the 
ratio of flux transmitted to the incident 

Photographic Units. 

In dealing with photographic materials 
it is proposed to adopt the word " phot " 
as a basis on which to build terms, in the 
same way as " lumen " is embodied in 
terms relating to visual response. The 
terms " photic " will be used in reference 
to photographic materials in the same 
manner as " luminous " is applied to 

capacity for producing visual sensations. 
" Photic flux " and " Photic efficiency -: 
etc., will be similarly used. The funda- 
mental unit will be the " photon." 

(1) Photic Flux (G) is the rate of flow 
of radiation evaluated with reference to 
the photographic response and is ex- 
pressed in '" photons." The photon (p) 
is the flux emitted in unit solid angle by 
a point source of unit photic intensity. 

(2) Photobility (A) of radiation of a 
particular wavelength is the ratio of 
photic flux at that wavelength to the 
corresponding radiant flux. 

(3) Photocitu (?) is the product of the 
photobility at a given wavelength and 
the corresponding ordinate of the spectral 
curve of radiant flux, and is represented 
by the ordinate of the spectral curve of 
photic flux. This curve is called the 
" spectral photicitv curve " and varies 
for different Bources. 

(4) Photic Efficiency (\Y) of a source 
is the ratio of the photic flux to the 
radiant flux from the source and is ex- 
pressed in photons per watt. 

The final decision as to the best method 
of defining photographic terms analogous 
to luminous intensity, brightness, il- 
lumination, etc., depends on experimental 
work now in progress. For the time 
being the unit of exposure will be defined 
as follows : — 

(5) Exposure (E)*=Illumination (N) 
Time (t). 

(6) Density (D) is used as to denote 
the light-stopping power of a silver deposit 
and is defined by the equation : — 

D=log O=log ^r where F 1 =flux inci- 
dent on the deposit considered, F 2 =liux 
transmitted by the deposit, 0— opacity 
of deposit. As the deposit consists of 
particles of metallic silver embedded in 
a matrix ol gelatine the light is partially 
scattered and the value of density 
depends upon whether the measurement 
is made with parallel or diffused illumina- 

General Theory. 

The relations to be included in the 
evaluation of visual and photographic 
efficiencies include those between energy 

* As the letter E is commonly used to denote 
exposure, it is necessary to select another 
letter. N, to indicate illumination. 









Radiant Flux 



Luminous Flux 



" ] 







Luminous Intensity . . 



: c.7 









Luminous Efficiency . . 




Reflection Factor 




Transmission Factor . . 



Absorption Factor 



. — 

Photic Flux 


Photon . . 







Photons /Watt 













Time " 








radiated at various wavelengths and 
(a) wavelength, (b) retinal response, and 
(c) photographic response. In addition 
the relation (d) between transmission 
values and wavelength for the various 
media which must be interposed between 
the sources of illumination and the 
photographic plate require study. These 
functions may be tabulated as follows : — 

J=f(\)=spectral energy distribution 
of the illuminant. 

T=f(\)=spectral transmission func- 
tion of the media between 
source and photographic- 

V=f(X)— visibility function of the 

A=f(\l=spectral distribution of sensi- 
tivity for the photo- 
graphic plate (photo- 
bility) . 

Typical illustrations of such functions 
are shown in Fig. 1. 

Here curve C is the energy distribution 
of an incandescent lamp, D the visibility 
function of the human eye, B the spectral 
transmission of a typical sample of glass, 
A the spectral sensitivity ol the kine- 
negative film. The ordinates for glass 
transmission are the ratio of transmitted 
to incident light, for the visibility func- 
tion relative brightnesses of an equal 

energy source ; the ordinates of the 
photobility function represent relative 
sensitivities. In other cases the ordinates 
represent relative energy at the respective 

The visual efficiency of any illuminant 
is given bv :— 


Ja V a d A 

7 Jxd* 


The photographic efficiency of an 
illuminant is given by the expression : — 
J a A\ d\ 



J,\ d,\ 

The curves in Fig. 2 and Fig. 3 illustrate 
the great differences that exist between 
photographic and visual efficiency. Thus 
in Fig. 2, curve. L, with its maximum 
near 530 jx/j, is determined for a tungsten 
lamp operated at 22 lumens per watt, 
the distribution of energy being shown 
in curve J. V is the visibility of radia- 
tion. In Fig. 3 the photicity curve P of 
kine-negative films for such a tungsten 
lamp is shown. This has two distinct 
peaks at 465 \i\x and 560 /j/u. (In com- 
puting the photicity curve in this case, 
no account has been taken of absorption 
by such materials as glass lenses.) 



In Fig. 4 four typical distribution 
curves are shown, A for skylight, B for 
sunlight, C for a tungsten lamp at 22 
lumens per watt, and J) for a tungsten 
lamp operated at 7*9 lumens per watt 
(approx. 1*25 watts per candle). The 
distribution of energy in the spectrum 
of the quartz tube mercury vapour lamp 
is shown by the heavy vertical line at 

tometers " to which materials to be 
tested are exposed, provide a means for 
subjecting various portions of a photo- 
graphic plate to exposures of precisely 
known and variable values. If a plate 
is so exposed that successive areas 
receive exposures increasing by con- 
secutive powers of two it will be found 
on development that a series of spots of 

Fio. 1. — Showing sensitiveness of photographic negative material (a) ; transmission 
of glass (b) ; relative energy of source (c) ; and visibility curve (d) throughout the 


Hg and adjacent vertical lines of smaller 

Complete knowledge of the various 
functions discussed above would, enable 
us to calculate the photographic efficiencies 
of an illuminant used with any prescribed 
photographic material. But some of the 
functions are not precisely known and 
their quantitative determination is beset 
with difficulty. Hence it is easier in 
practice to determine relative efficiency 
by direct methods. 

Kelative Efficiencies of Illuminants. 

The methods used in determining 
relative photographic efficiencies are 
essentially those used to ascertain plate- 
speeds in " sensitometry." The " sensi- 

increasing opacity are obtained. By 
measuring the density of each spot, and 
plotting these densities against the 
logarithms of exposures, the " character- 
istic curve " of the plate is obtained. 
The curves shown in Fig. 5 were thus 
obtained. The curve AB was obtained 
from a strip developed for three minutes 
in a standard developer, that designated 
by A 1 B 1 by a six-minute development. 
It is customary to express the blackness 
or opacity of a photographic deposit in 
terms of its density (B). The part of 
the curve between A and B is a straight 
line which, when extended, cuts the log 
exposure axis at 0, and the value of the 
exposure at O is termed the " inertia " 
of the plate. The extension of A' B 1 
meets the axis at the same point, thus 



showing that inertia is independent of 
time of development. This, however. 
is true only under certain conditions 
dependent on the constitution of the 
developing solution. 

Inertia is commonly expressed in 
terms of exposure (the product of time 

As inertia is expressed in visual units, 
it will depend on the quality of lighl used 
during the exposure. Thus if the plate 
is only sensitive to blue fight (a* 
practically the case for ordinary photo- 
graphic materials) a lower inertia will be 
obtained with blue light than for light of 






















F(G. 2. — Showing visual efficiency of tungsten 
lamp (l), with visibility curve (v) and energy 
curve (j). 













- — v. 



400 w?lu<™ m 

Fig. 3. — Photicity curve for tungsten lamp (p) 
and energy curve (j). 














Fru. 4. — Typical energy distribution curves 
for skylight (a), sunlight (b), and tungsten 
lamps (c and d). 

/■ — 

.x* - 



t y ~T' 

1 7 Z&'Jl^ 

8 £* .,' 

: .. A+* :_b ;." 




log exposure 

Fig. 5. — Relation between density and 

of exposure, (t) and illumination (NJ 
incident on the plate). Illumination is 
usually expressed in metre-candles, time 
in seconds. The reciprocal of the inertia 
is proportional to the sensitivity or Bpeed 
of " Speed-numbers "' of plates are ob- 
tained by multiplying the reciprocal of 
inertia by some arbitrarily chosen con- 

a yellow tint. Hence determination of 
inertia, as defined above, offers a con- 
venient means of comparing photographic 
efficiencies. If the same plate-speed is 
used throughout the reciprocals of the 
inertia values will be directly propor- 
tional to the photographic efficiency of 
the various sources. 

This is illustrated in Fig. 6 S where A is 



,i curve obtained with a high-efficiency 
tungsten lamp and B a curve obtained 
under similar conditions with a carbon 
lamp. Tin- inertia value for curve A is 
only half that for curve B, and it is 
inferred that, for a given exposure, the 
photographic effect of the tungsten lamp 
will be twice that of the carbon lamp. 



1 1 

1 1 

1 I 

• 1 

J 2 

* J 

If i 


I'n. 6. Relating density and exposure. 

In making such comparisons it is 
convenient to choose some source as a 
standard. It seems logical to adopt the 
light of the sun, seeing that most ordinary 

photography is done by daylight. (This 
argument has less force when applied to 

kinema studios, but as it is undesirable 
to have two standards of comparison, 

it seems advisable also to retain sunlight 
as the standard in this ease.) 

In Table 2 are collected the result- of 
measurements made with a large number 
of different sources using the three 
typical classes of photographic materials. 
The ordinary plate is sensitive only to 
blue light, while the orthochromatic is 
sensitive to both blue and green, and the 
panchromatic to blue, green and red. 
The values for each photographic material 
in the column " S " are the reciprocals 
of inertia values. Values in the column 
"W v " are relative efficiencies in terms 
of sunlight as 100 per cent. These 
efficiencies are in terms of visual units : 
tor instance, a value of 50 indicates that 
with the source to which this value applies 
the illumination on an object must be 
twice as great as it would have to be 
with sunlight in order to obtain a given 
photographic, effect. Since efficiency in 
terms of energy consumption is also of 
considerable interest values on this basis 
are also given in Table 3. 

Whereas, in Table 2, the photographic 
efficiency (W v ) was determined by con- 
sidering the intensity of illumination 
necessary to obtain a certain photo- 
graphic effect, the photographic efficiency 
in Table 3 (W,.) is based on the energy 
incident upon the plate in order to 
produce a given photographic effect. If 
the inertia value is expressed in terms of 
ergs consumed at the source per sq. cm. 
of plate, the reciprocal of this quantity 
is proportional to the photographic 
efficiency of the source on an energy 
basis. If sunlight is taken as the 
standard as before, and assigned an 
arbitrary value of 1<mi, then: — 

100, i.e. (for sun) 


i.e. (for source considered) 

In the c ;1 se of electric incandescent 

lamps the quality of light emitted de- 
pends upon the temperature of the 
filament and photic efficiency is thus 
affected by the voltage. It seemed 
worth while to ascertain photic efficiency 
for a .")i"i watt gasfilled lamp operated 
at various voltages giving visual efficien- 
cies from '_' I up to 25'0 lumens per watt. 
The results are assembled in Table 4. 


Source: Gasfilled tungsten: Watts. 500. 

Volts, 120. Reduction factor, 88. 

Exposure : 15 metre-candle seconds : 
lllumination=0-10 m.c. Time = 150 sec. 

Photographic Material. 

y lumen 


< >nliiiarv 



\ watts 



























7 J 


In the first column of Table 4 the visual 
efficiency (C) is given. In the three subse- 
quent Tables W is given for the various 
photographic materials, computed on the 
basis of equal visual intensities, taking 



Relative Photographic Efficiency =Wv. 



ographic Materials. 


\ watt / 







I j Sun 





2 Sky 





3 Acetylene 





4 Acetylene screened 





5 Pentane 






Mercury arc — quartz 






Mercury arc — nultra glass 






Mercury arc — crown glass 






Carbon arc — ordinary 






Carbon arc — white flame . . 






Carbon arc — enclosed 






Carbon arc — ■" Aristo " 






Magnetite arc 






Carbon glow lamp 





Carbon glow lamp 






Tungsten evacuated 





Tungsten evacuated 





16 Tungsten nitrogen — tilled 





Tungsten nitrogen — filled 






Tungsten blue bulb 





Tungsten blue bulb 






Mercury- vapour 





Relative Photographic Efficiency = \\\ 



Dgraphic Materials. 




V watt / 

























Acetylene screened 












Mercury arc — quartz 






Mercury arc — " nultra " . . 






Mercury arc — crown 







Carbon arc — ordinary 







Carbon arc — white flame . . 






Carbon arc — enclosed 






Carbon arc — " Aristo " . . 







Magnetite arc 






Carbon glow 





Carbon glow 






Tungsten vacuum 






Tungsten vacuum 







Tungsten nitrogen 






Tungsten nitrogen 






Tungsten blue bulb 






Tungsten blue bulb 







• | 







sunlight as 100. It will be noted that 
photic efficiency increases appreciably 
with rising voltage 5 and in some i 
it may be expedient, during photographic 

exposure, to operate such lamps at a 
higher voltage thai) that for which they 
arc normally used. 

During recent years many different 
types of (lame carbons have been placed 
on the market, and in this way marked 
variations in quality of light may be 

tn ascertain the relative efficiencies for 
three-colour work. A current consump- 
tion of 25 amperes with a potential of 
50 volts across the arc was considered an 
average condition and adhered to 
throughout. The arc was operated on 
UOv. and a plain cored negative was 
used above with a in mm. flame carbon 
below. Sensitometric measurements were 
made using unfiltered light and with 
each of tlic three standard tri-colour 

TABU". 5. 

No Filter. 



(oven (58). 



Efficiency . 






i W, 




I ;,i i 









White Blame Arc 










Pearl Flame Arc 










Yellow Flame Arc 





40 : 





Red Flame Arc 










Blue Flame Arc . . 










High Intensity White 
Flame Arc 










TAB 1.1 ... 

No Filter. 



Green (58). 









































































High Intensity White 










obtained. In some branches of kine- 
matography this control of quality is of 
considerable advantage, for example, in 
taking coloured films. The same applies 
to photo-engraving. In both cases 
colour-filters must be used, ' and it is 
possible that an arc emitting strong 
radiation in certain regions would be ad- 
vantageous. Measurements with several 
different types of flame carbons weir 
accordingly made, panchromatic plates 
being used throughout as it was desired 

taking filters, Wratten No. 25 being the 
red, No. 58 the green, and No. 49 the 
blue. The values of relative efficiency 
on the basis of equal visual values given 
in Table 5 are interesting. The values 
in column 1 refer to an unfiltered arc, 
those in columns 2-4 to the filters as 

Corresponding values of efficiency on 
the basis of equal energy consumption 
are presented iu Table 6. 

(To be continued.) 




In a paper by X. Campbell and B. P. 
Duckling appearing in the Philosophical 
Magazine, the authors point out that 
in order to establish a scientifically or 

legally satisfactory system of measuring 
any physical magnitude it is not sufficient 
to state the units to be employed. It 
is necessary also to state the laws of 
measurement. Photometry provides an 
exceptionally favourable illustration of 
this necessitv. 

International congresses have fixed with 
great elaboration the units of certain 
practically important physical quantities. 
The results of their labours are embodied 
not only in scientific treatises but in 
much national legislation. But the 
authors contend that a statement of the 
laws of measurement should be included 
with a description of the units in any 
defining legislation. 

In photometry the inverse square law 
is treated inadequately. In particular 
it is assumed to be a primary and neces- 
sary law for the measurement of illumina- 
tion, whereas one photometric magnitude 
at least can be defined without reference 
to it. Another defect is the absence of 
any clear statement of the addition of 
illumination. Moreover, the significance 
of magnitudes is made to depend on a 
theory that illumination is due to the 
incidence of something called light — 
which is wholly unnecessary. 

Light measurements are based on 
judgments of equality of brightness, by 
observations of photometric surfaces 
(P.S.) which are members of pairs. If 
their positions are interchanged equality 
of brightness should be undisturbed. 
They should preferably be white, matt, 
and non-luminous. Some surfaces nearly 
fulfil these conditions and are best suited 
for photometry. An assumption of 
equality of brightness assumes that the 
P.S. are perfectly matt, a condition that 
cannot be realised in practice. Hence 
the judgment of equality of brightness 
may depend on the directions from which 
the P.S. are viewed. Tin' permissible 
range of variation therefore requires 

* Abstract of a contribution by N. Campbell 
and B. P. Duckling to the Philosophical Maga- 
zine, September, 1922. 

The law of addition is not invariably 
true when applied to illuminations. If 
the sources yield light of different colour 
the results of addition may be affected 
by the Purkinje and allied phenomena. 
The inverse square law, as applied to 
photometry, can be stated in the follow- 
ing form : — 

" The. illumination on a surface A 
from a source X is inversely proportional 
to the square of the distance of X from 
A so long as (1) X and A are "points " 
(2) the angles between the line XA and 
any lines characteristic of X and A re- 
main the same ; (3) the medium between 
X and A (or rather the variable part of 
it) is perfectly uniform and transparent ; 
(4) that the bodies surrounding X and 
A are perfectly black." The authors 
suggest a method by which the inverse 
square law can be satisfactorily proved. 
This law enables us to define a derived 
magnitude, namely the constant product 
Ir 2 . We might also derive a new product 
Ir 2 . sec0., which would depend only on 
the source and the direction of the P.S. 
relative to it. It is often useful to invert 
the relation arrived at and to express 
intensity and illumination in terms of 
flux. But we know nothing about flux 
until we have measured illumination. 

The authors next proceed to discuss 
brightness pointing out how the con- 
ceptions of this quantity depend on where 
the surface illuminated is perfectly diffus- 
ing or not* They also refer to various 
subsidiary laws of measurement, such 
as those assumed in measurements of 
intensity with a sphere photometer. The 
notation proposed is compared with that 
adopted by the Standards Committee of 
the Optical Society of America :— 

The Authors* Notation. American. 


.. I 

Flux Density 

.. D 


. . * 

Intensity . . 

.. C 

Flux . . 

.. F 


.. F 


.. B 


.. B 

It will be noted that there are appreci- 
able differences. The authors also object 

* The authors speak of such a surface as 
obeying " Lambert's Law," but we believe 
that, according to Mr. Trotter, Lambert's Law 
relates only to illumination, and has nothing 
to do with the nature of the surface. — Ed. 



to the American definition of the Lam- 
bert, where, they suggest, '" one lumen 
per steradian " should be substituted 
for " one lumen." The statement that 
" one candle per square centimetre equals 
3" 1 4 1 fi lamberts " is also objected to. 
In the first place lamberts have only been 
defined for surfaces obeying " Lambert's 
Law."' and Borne specification of the 
direction in which intensity is measured 
is necessary. If a direction normal to 
the surface is assumed a surface of one 
sq. cm. emitting an intensity of 1 candle- 
power has a brightness of 1 lambert, not 
tv lamberts as the American Committee 
affirm. It the surface is plane and obeys 
Lambert's Law the average intensity 
over this hemisphere is \ candlepower 
per sq. cm. and the brightness of a 
surface emitting I mean candlepower 
pi i s(|. cm. would be equal to 2 lamberts. 
The simple and obvious convention giv- 
ing the result that 1 candlepower per 
sq, cm. equals one lambert is preferred. 


Some further particulars of the neon 
(" Osglim ") discharge lamp, which has 
already been described in The Illuminat- 
ing Engineer,* were given in a paper by 
Mr. J. W. Ryde, recently published in 
the Photographic Journal. 

Equipped with a ruby glass or ruby- 
stained bulb this lamp, which yields only 
red and orange rays, appears to be a 
safe type for use in the photographic 
dark room. Mr. Ryde stated that a mix- 
ture of neon gas with 20 per cent, helium 
is used in the bulbs. The discharge is 
stabilised and the current cut down to 
about 20 milliamperes by the use of a 
series resistance of a few thousand ohms, 
wound on a small spool and concealed 
in the brass cap. Without such a re- 
sistance the current would quickly rise 
to a high value and an arc would form 
between the electrodes and quickly 
destroy them. The necessity for using 
such a high resistance, however, no doubt 
<ioes far to explain the relative low 
efficiency of the lamp. Possiblv im- 
provements in this direction may be 
effected in the future. 

* Illuminating Engineer, December, ln^l, 
page 243. 

As there are no fragile filaments the 
lamps are robust and should have a very 
long hfe but for the ultimate blackening 
of the bulb. This blacken : ng is kept 
within limits by the introduction of 
• el tain minute gaseous impurities where- 
by, it is stated! a life of 1,000 to 2,000 
hours can be obtained before blackening 
of the bulb becomes serious. 

When once the discharge has started 
the current through the lamp increases 
almost lineally with the voltage over 
the working range. It is stated that 
the candlepower has been found to be 
almost proportional to the current pass- 
ing through the lamp, and is given by 
the relation : 

m R 

where 1 -current in amperes, E = vol- 
tage of supply. H value of Beries resist- 
ance, A=area of cathode in sip cms., e, 
M, and k are constants. For the neon 
discharge lamp M is approximately 10 -4 , 
e is about 150, k is about 12 candles 
per ampere. 

According to this relation the standard 
lamp, taking about 20 milliamperes. 
would yield about 0*25 c.p. 


We have received from the Electro- 
Harmonic Society particulars of the 
programme for the coming season. It 
is interesting to note that the Concerts 
will now be held at the Caxton Hall, 
Westminster, instead of at the Cannon 
Street Hotel. The dates of the Concerts 
are as follows : — 

Smoking Concert. — Wednesday, 11th 
October, 1922. 

Ladies' Night.- — Tuesday 14th Novem- 
ber, 1922. 

Smoking Conceit. — Tuesday, 12th 
December, 1922. 

Smoking Concert. — Wednesday, 10th 
January, 1923. 

Ladies' Night. — -Wednesday, 14th Feb- 
ruary, 1923. 

Smoking Concert. — Wednesday. 14th 
March, 1923. 

Those interested should communicate 
with the Hon. Secretary, Mr. W. E. Lane. 
£86, Finsbury Pavement House, E.C.2. 




The lighting of the St. James's Park 
New Road is an interesting modern ex- 
ample of the illumination of a public 
thoroughfare by gas. 

The New Road runs from Storey's 
Gate to the Duke of York's Steps, lead- 
ing past the site for the Guards Memorial, 

A night view. 

which will face the centre of the Horse 
Guards Parade. 

The total number of lamps in this 
thoroughfare is ten, of which two are 
placed ready in position to light the 
Memorial itself when it is erected, one 
being situated on either Side of the exact 

The lamps and columns were specially 
designed by H.M. Office of Works, and 
were supplied by the Gas Light and Coke 
Company, who carried out the installation. 

Each lamp contains a cluster of 1(3 
W'm. Sugg and Go's Super-heated Burners, 
which are supplied with gas at ordinary 
pressure, and provide an illumination of 
approximately 1,000 candle power. The 
burners are of medium size, consuming 
about 2^ feet per hour each, or a total 
of 35 cubic feet per lamp. 

View by daylight. 

The lamp columns are approximately 
180 ft. apart and the height from the 
2'round to the mantle is 22 ft. 

A separate supply to a pilot light has 
been run to each lamp, and the lighting 
and extinguishing is carried out by the 
operation of a tap, which is situated in 
the base of the column. 

Some photographs are attached, illus- 
trating several of the lamps. The one 
taken by night gives an idea of the 
general illuminating effect. 


It is announced that the 169th session 
of the Royal Society of Arts will be 
opened on "Wednesday, November 8th, 
at 8 p.m., when an address will be de- 
livered by the Chairman of Council, Lord 
Askwith. The Society is now the owner 
of its House, which has been undergoing 
extensive alterations and renovation. 
The amount Contributed to the Building 
Fund so far is £42,726 os. 4<L, but nearly 
all the cost of renovation, about £7,000, 
remains to be raised. It would be a 
great satisfaction to the Council to feel 
that the Society could continue its work 
unhampered by fresh financial obligations 
and Fellows are reminded that the Sub- 
scription List is still open. 

There are a number of interesting 

items for the coming session. Among 
the papers before Christmas we note 
those by Bailie William Smith on " The 
Economy of Smoke Abatement " (Nov- 
ember 22nd), by Major E. W. S. Turner 
on "The Hot Wire Microphone and its 
Applications" (November 29th), and by 
Sir Sidney G. F., Director of the 
British Museum of Natural History, on 
''The Fading Of Museum Specimens" 
(December 1:5th). Prof. W. A. Bone is 
to deliver three Cantor Lectures on 
'" Brown Coal and Lignite.*' 

Papers after Christmas include " Heat 
Resisting Glass," by Prof. W. E. Turner. 
Mr. S. S. Cook will deliver three Howard 
Lectures on '" Recent Improvement in 
Steam Turbines," and the Dr. Mann 
Juvenile Lectures on " The Spectrum, 
its Colours, Lines and Invisible Parts " 
will be given by Prof. Charles S. Darling. 





A useful contribution by Mr. J. 1!. Col- 
ville in a recent i>Mir of the Gemini 
Electric l!< view (U.S.A.) summarises some 
of tin- main principles in industrial 
lighting. It is interesting to hear that 
" in the last year <>f the war and in the 
v«-ar immediately following, more pro- 
was made in the application of 
artificial lighting than in any ten-year 
period preceding." This is ascribed to 
the influence of experiments conducted 

under actual working conditions. I 
have shown that remarkable incri 
in productive power were possible when 
industrial plants were provided with 
artificial illumination comparable with 
that obtained with daylight under the 
best conditions. Once tin- traditional 
illumination levels were broken through 
and values three or four times as high 
actually tried out in practice, tin- handi- 
cap imposed by previous standards 
became apparent. 

The following chart for analysing 
lighting conditions is presented : - 

Good lighting 

Goon Lighting. 
Good lighting requires three things : 

1. Light of suitable quality. 

2. Light of the proper direction. 
.'*. light in the correct amount. 

["Absence of glare. 

Suitable quality «j Absence of reflected glare. 

^Proper colour. 

t> i- f Shadows soft and luminous. 

Prone direct ion < n .• ,■ . •■ . . 

1 \ I inform distribution. 

f Lighting for safety. 

Correct amount <{ Li f htin ^ f ° r economical produc- 

(_ Proper cleaning of units. 

( 'ause. 
Bare lamps. 

Miscellaneous local lights 
dangling on «1 r< >;« cords. 

General system — Units too 
fa i apart or too low. 

clear Lamps where polished 

laces are presenl on material 

or machinery. 

Too little illumination. 

Sharp, black shadows. 

Gloomy and cheerless ap< 
pearance of room. 

Bad LiOHnxo. 


Glare, eyestrain, wasted light, 
harsh shadows. 

Glare, eyestrain, danger oJ 
accident particularly about 

belting and moving machinery. 
short circuits, breakage. 


The modern efficient type °f 

General overhead system. 

" Spotty " lighting ; areas be- Proper relation between 
twecn lamps receive very little mounting height of units and 
light ; shadows are very black, spacing distance. 

Reflected glare, eyestrain. 

Equipment to diffuse down- 
ward light from filament. 

Time lost by employees ; eye- Larger lamps in suitable re- 
strain. Accidents; no incentive {lectors spaced closer together 

to keep place cleaned up. 

Accidents ; time lost ; eye- 

if necessary. 

Modern equipment properly 


Dusty, dirty. 


or broken 

Unpleasant contrast between Liberal use of white paint ac- 
light sources and background ; companied in some cases where 
dispirited employees. location is suitable by use of 

glass reflectors. 

Loss of 40 per cent, to 60 Institute a regular cleaning 
per cent, of the light paid for. schedule. 



In addition the author includes in the 
article several effective illustrations of 
the drawbacks of bad lighting, which 
are shown in Figs. 1-4. 

It is striking to observe what high 
values of illumination are becoming 

candles still produce a further improve- 
ment. Another feature is the quickening 
of vision at these high illuminations. 

In the subsequent portion of the article 
importance is attached to avoidance of 
troublesome shadows, uniformity of 

Direct glare. 

Reflected dare. 

Figs. 1 and 2.— A brilliant source of light is not necessarily good lighting. Either direct glare or 

indirect glare is harmful. 

Fig. 3. — Deep black shadows are troublesome 
and a source of constant danger because of 
what thev mav conceal. 

Fig. 4. — Lighting equipment should be 
thoroughly cleaned at frequent intervals. 

customary in the United States. W c 
know that 3 or 4 foot-candles will enable 
us to see more detail than will 1 foot- 
candle. But 10 foot-candles will reveal 
more than 3 or 4, and according to Mr. 
Colville, advances to 50 or even 100 foot- 

illumination and regular maintenance. 
Surveys of installations show that de- 
preciations of 50-60 per cent, or more 
arise when lamps are not periodically 
renewed and bulbs and fittings are 
allowed to become dirty. 





By H. W. Bookob 

In a recent issue of the Transactions of 
the American Illuminating Engineering 
Society there is an interesting account 
of the lighting of the Milwaukee Art 
Institute. The good results are ascribed 
mainly to the sympathetic co-operation 
of building committee, architect and 
illuminating engineer. The building com- 
prises a variety of rooms, but the method 
employed in the main gallery is of chief 

It is common knowledge that the 
avoidance of troublesome reflections in 
the glass of pictures forms one of the 
greatest difficulties in the artificial light- 
ing of picture galleries. 

If so-called general lighting with diied 
units is employed a portion of the picture 
is apt to be blotted out by images of the 
light-sources when seen from certain 
positions. Similarly, with indirect light- 
ing, an image of the bright ceiling causes 
trouble. The only practicable means of 
avoiding these reflections is to illuminate 
each picture by light falling upon it 
at an acute angle (less than 30°) with the 
picture surface. In addition it is desir- 
able that the walls on which pictures are 
hung should be evenly lighted — a con- 
dition difficult to realise with trough 
reflectors, which tend to overlight the 
upper portions of the wall and underlight 
the lower portions. Yet another re- 
quirement is that the illuminated pictures 
should be the centre of interest, the walls 
being more brightly lighted than any 
other objects falling within the field of 
vision. Other considerations are that 
the quality of light should approach that 
of daylight so as to reveal colours 
correctly ; that unsightly shadows should 
be avoided ; and that the lighting must 
be reasonably easy to install and keep 
clean. Finally there is the problem of 

and A. J. Sweet. 

installation and maintenance cost. The 
means adopted in this gallery may 
be briefly described as follows. About 
30 inches directly above the skylight 
and along a line somewhat above and 
in front of the pictures on the walls, 
a row of 150 watt 1,400 1. C, (daylight) 
lamps are mounted, each lamp being 
equipped with a suitable reflector so 
tilted that the maximum light is directed 
towards a point 36 inches above the floor. 
The skylight glass is of ribbed crystal 
so as to give sensibly even illumination 
along any horizontal line on the wall. 
and the relative position uf wall and 
reflectors is so adjusted that the illumina- 
tion vertically is also practically uniform. 
In this way it is considered that the 
requirements referred to above were sub- 
stantially met. However, the cost of the 
reflectors with holders and supporting 
framework was somewhat high, namely 
25 dollars per unit. The paper also tun- 
tains a description of the method of 
lighting in the various minor galleries 
and offices, etc. Perhaps one of the most 
interesting items was the method of light- 
ing the Director's office, situated in the 
basement with only a very narrow window 
near the ceiling to admit daylight. It 
was decided to replace this completely 
by an artificial daylight window consist- 
ing of a cabinet with a glazed glass door, 
behind which sixteen 150 watt C, lamps 
were mounted. 

The entire lighting system was pro- 
vided and installed at a cost of 5,100 
dollars (approx. £1,000), including archi- 
tect's and engineer's fees. The relatively 
small cost was made possible only by 
the sympathetic co-operation of deference 
to each other's rights of decision on the 
part of the building committee, architect 
and illuminating engineer. 

* Abstract of a paper read before the Uluininating Engineering Society, U.S.A. 




— • • • • • ~- 

[At the request of many of our readers we have extended the space devoted to 
this Section, and are open to receive for publication particulars of interesting 
installations, new developments in lamps, fixtures, and all kinds of apparatus connected 
with illumination. 

The contents of these pages, in which is included information supplied by the 
makers, will, it is hoped, serve as a guide to recent commercial developments, and we 
welcome the receipt of all bona-fide information relating thereto.] 


A booklet issued by the General 
Electric Co., Ltd., gives full particulars 
of the latest types of Osrarri automobile 
lamps, which have several interesting 
features. The filament is of a very 
concentrated type, so as to approach 
as nearly as possible the ideal point - 
source and enable the maximum benefit 
to be obtained from parabolic reflectors. 
Another feature is the tapering of the 
bulb towards the cap, enabling the lamp 
to be placed far back in reflectors for 
focusing purposes. With the same ob- 
ject the caps are withotit shoulders. 
The cement used for attaching the caps 
is also of a special white colour which 
has good reflecting properties. 


An ingenious little card (priced Is.), 
issued by Mr. A. E. Bawtree (7, Manor 
Road, Sutton), enables English measures 
to be converted into metric units or vice 
versa with considerable ease. Instead of 
the somewhat involved tables sometimes 
applied, the method of allotting a double 
graphical scale for each conversion is 
adopted. With a little practice this 
method is doubtless easier to apply. 
The scales relate to linear, surface and 
cubic values and weights, and there are 
several supplementary scales connecting 
Centigrade and Fahrenheit temperature, 
and relating radius to circumference, 
which should prove useful. 


In the course of a recent visit to the 
showrooms of Messrs. Falk Stadelmann 
& Co., Ltd., we had an opportunity of 
inspecting several novelties in connection 
with " Veritas " burners. Of these 
special interest attaches to the new patent 
gas adjuster. As is well known, some 
forms of gas adjusters are apt to give 
trouble chiefly because they are too 
sensitive — i.e., a relatively slight move- 
ment of the thumbscrew causes too great 
a variation in the inlet of gas. For the 
same reason such adjusters are apt to be 
affected by vibration, as a slight change 
of position at once alters the amount of 
gas passing. 

In this new adjuster, therefore, the 
motion is made much slower and more 
uniform. A number of turns of the screw 
are needed before the entrance of gas is 
very markedly affected, and the move- 
ment is quite easy to control. The new 
adjuster is fitted to a variety of burners, 
including the " three-cluster " types 
which are considered to represent the 
latest thing in economical gas lighting. 
These burners are made of heavy gauge 
aluminium and are stated to be free from 
corrosion and oxidation. Two main types, 
the " Veritas-Trilux " (for three Bijou 
mantles, yielding approx. 150 c.p.) and 
" Super-Veritas " (for three No. 2 man- 
tles, yielding approx. 300 c.p.), are 
listed. Vitreosil chimneys can be used 
with these burners ; or, alternatively, 
there are available globes of heat-resisting 
glass, which we understand can be made 
in the opaline as well as the clear variety. 

Attention is also drawn to a very simple 
and inexpensive single brass burner with 
china deflector (the improved " Vincit " 




An Effective Demonstration at Croydon. 

At the invitation of the Croydon I ; a< 
Company we were recently afforded an 
opportunity of inspecting the gas-lighted 
and heated bungalow, which the Com- 
pany have installed in the premises of 
Messrs. Allders, Ltd. (North End, Croy- 
don). The bungalow forms a distinct 
section on one of the upper floors, with 
a pleasing exterior of white plaster and 
red tiles, and trailing Virginia creeper 
in autumn tints. The interior gompi 
a suite of small rooms, all equipped to 
show and illustrate the latest domestic 
applications of gas. The lighting is 
naturally the point of chief interest to 
this Journal. It was very satisfactory 

to see that soft and well-shaded lights 

weir the rule. Super-heated pleasing 
inverted burners with vitreosil glassware 
are used throughout, the small bracket 
lights used in ili'- bathroom being par- 
ticularly workmanlike. In the drawing 
room, dining room, bedrooms and nursery, 
burners, besides being equipped with 
vitreosil chimneys, have supplementary 
external silk shades, some of very 
charming colours. The dining room uses 

the conventional circular shade over the 
table, in the drawing room a cluster of 
three orange silk shade- provides central 
lighting, and there are also local lights*. 
Throughout the bungalow, distant con- 
trol by pneumatic switches is introduced, 
and it was shown how. by means of a 
single switch, any combination of three 
central lights could be obtained. This 
method of distance control is now- 
considered quite reliable. It naturally 
requires occasional supervision, but con- 
sumers who accept maintenance from 
the gas company should have little 

In the small bedrooms, two lights, one 
over the dressing table, the other beside 
the bed. were provided. A feature in 
these rooms was the complete harmony 
of the colours of the silk shades with 
those of the eiderdown, wallpaper and 
crockery. These silk shades give very 
soft and pleasing effects. The only 
criticism one might be disposed to make 
is that a somewhat large proportion of 
light is allowed to pass out through the 
silk surface. It would, however, be 
quite easy, by introducing concentrating 
reflectors within the shade, to increase 
the useful downward component. 

The nursery struck one as a par- 
ticularly charming room, the light wall 
bearing coloured panels with " Peter 
Pan " pictures, which were also executed 
on the lamp shades. 

Although we have referred above 
chiefly to the lighting arrangements, it 
must not be assumed thai heating and 
cooking were overlooked. The kitchen 
is equipped very completely with gas 
range and oven, etc., and the bathroom 
with all the latest methods of obtaining 
hot water. The projecting Btove, set in 
a large brick fireplace in the drawing 
room had a cheerful appearance. We 
are informed that the Company is pre- 
pared to enamel the ironwork of gas 
Stoves in any desired colour to match the 
fire-place tiles or other decorations. 

We understand that the exhibition 
has proved very popular, and on the 
occasion of our visit, just before closing 
time, there was still a constant stream 
of v isitors. 


The Western Electric Co., Ltd., have 
appointed Lionel Robinson & Co., Sole 
Selling Agents for London. Middlesex 
and Surrey, for their B.A.G. Diffusers. 
A range of samples is on view at the 
Company's showroom at .'5. Staple Inn, 
W.C.I, and catalogues are now being 

sent out to the trade. 


Henry Wiggin & Co., Ltd.. Birming- 
ham, are announcing considerable re- 
ductions in the prices of their well-known 
"Ferry" resistance wires and "Glow- 
ray," l!e.lra\ " and " Brightray " 
nickel chromes for cooking and heating 
apparatus. Details can be Obtained from 
the sole selling agents for the United 
Kingdom Lionel Robinson & Co., 3, 
Staple Inn. Holbora, W.C.I. (Phone: 
Holhorn 6323.) 


We are informed that Messrs. Viekers, 
Ltd., have succeeded in securing new 
work for their Barrow establishment in 
the form of a first-class passenger liner 
of approximately 20,000 tons measure- 
ment for the Orient Line. The pro- 
pelling machinery will be turbines, driving 
through single reduction gearing and the 
boilers will be arranged for oil fuel. 
When completed the vessel should be a 
handsome addition to the fleet of ships 
operated by the Orient Line and will 
take up service between Great Britain 
and Australia. 



View of nursery lighted by pendant with large inverted burner, silica cylinder and shade 
in centre of room, controlled by switch. Blue enamelled fire and tiled surround, 
with " nursery " fire-guard. Pedestal boiling burner connected to fire-supply. 

A view of the lounge lighted by 3-light central silver pendant with medium inverted 
burners, silica cylinders and gold shades, and by four silver brackets similarly 
equipped. In the background is seen a " Sunbeam " gas-fire in rough red brick 





These new metal reflectors (issued by 
Astro Electric, Ltd.) are of a very simple 
type, a feature being their light weight 
such that, in the smallest form (Type 
A), they can be dropped merely into place 
on the lamp bulb. The larger types are 
mounted on a Lamp holder in the usual 
way and either allow a space for ventila- 
tion (incidentally also allowing a small 
amount of light to pass upward) as shown 
in Fig. J. or arc of the enclosed type 

Fig. I.— Typed. 

(Fig. 2). It will be observed that in 
either case the reflector is brought quite 
close to the filament. It is stated that 
t his has no prejudicial effect on the special 
"pearl silver" reflecting surface, which 
is protected with clear Lacquer so as to 
be untarnishable. 

This inner surface may be described 
as "semi-polished" and consists of 
minute irregularities which serve to dif- 
fuse the light. A metal surface of this 
kind, when brought quite near to the 
filament, is doubtless favourable to great 
concentration of light. According to a 
test made at the Faraday House Testing 
Laboratory the illumination under the 
pip of an ordinary straight filament 

tungsten lamp was increased 33J times 
by the use of one of these reflectors. 
One quality which this reflecting surface 
appears to possess is the elimination of 
striations from the lamp filament — a 
troublesome defect that is notoriously 
apt to occur with polished and semi- 
polished reflectors. 

One of the most plea-sing arrangements 
which we witnessed was the combination 
of these reflectors with the " FuJlo- 

Type E. 

lite " (i.e.. opal glass bulb) gasfilled lamps. 
The inner surface of the reflector is so 
brightly illuminated as to become almost 
indistinguishable from the actual bulb. 
We were also pleased to observe that the 
majority of these reflectors are so designed 
that the lower rim comes well below the 
pip of the bulb, the filament being thus 
effectually screened. Some types (such 
as Type E illustrated above) are fitted 
with a telescopic tube extension allowing 
the relative position of lamp and re- 
flector to be adjusted — a useful device 
in view of the variety of shapes and 
sizes of lamps at present on the market. 


In view of the prospect of broadcasting 
in London, much interest is being taken 
in wireless telephony, and the apparatus 
enabling the user to " listen in " to the 
entertainments provided by the broad- 
casting centres. We have received from 
Messrs. Falk Stadelmann & Co., Ltd., a 
list of the simple wireless receiving sets in 

which the receiver is of the crystal type. 
It is stated that the receiving sets 
illustrated will take in speech and music 
within a radius of at least twelve miles 
from a broadcasting station, and up to 
approximately twenty-five miles under 
favourable conditions. Valve sets are 
also in preparation where apparatus of 
greater effective radius is required, of 
which a separate pamphlet will be pub- 
lished when ready. 



INDEX, September, 1922. 

Editorial. By L. Gaster .. 

Gas Lighting in the New Road, St. James's Park 

Industrial Lighting, Fundamental Principles in. By J. R. Colville 

Kinema Studios, The Use of Artificial Illuminants in. By L. A. Jones. . 

Light, The Measurement of. By N. Campbell and B. P. Duddinu 

Milwaukee Art Institute, The Lighting of. By H. W. Bogxok and 
A. J. Sweet 

Neon Discharge Lamps 

Reviews of Books and Publications Received 
Royal Society of Arts, Sessional Arrangements 
Topical and Industrial Section : — 

An All-Gas Bungalow — New Gas Burners — Astro Reflectors — Electrical 









Research in the Metals Industry. 
An interesting pamphlet has been issued 
by the British Non-Ferrous Metals Re- 
search Association (71, Temple Row, 
Birmingham), covering many problems 
met with in the use of copper, brass, 
aluminium, nickel and lead. The ex- 
periments on improvement in brass, 
metal polishing and soldering deserve 
special notice. Other work in prospect, 
when additional financial support is forth- 
coming, will bear on various problems of 
importance to the electrical industries, 
to die casters and to the tin-plate trade. 

The Reconstruction of Europe. 
We understand that Sir Ernest Benn's 
scheme for the publication of an English 
newspaper in Vienna has at length 
materialised and the first issue of the 
European Commercial has now appeared. 
The matter is written by English journa- 
lists under an English editor, and it is 
hoped to present new information about 
European affairs not ordinarily acces- 
sible to the British public. The paper 
aims at promoting commercial intercourse 
between the two countries, and this new 
venture deserves attention. 

Returns of Gas Undertakings in the 
United Kingdom. (Published by H.M. 
Stationery Office, Imperial House, 
Kingsway, London, W.C.2.) 

Two publications relating to gas under - 
takings, issued by H.M. Stationery Office, 
make a timely appearance. One of these 
relates to undertakings belonging to 
local authorities (7s. 6d. net), the second 
publication to undertakings other than 
those of local authorities. The data 
given appear to be very complete, the 
rates charged for gas supply, the receipts 
and expenditure, gas -production and 
consumption, amount of coal used, and 
also the number of public lamps supplied 
are stated for each concern as well as 
financial particulars. These data shorild 
be very useful to all concerned with gas 
su PPly- The returns relate to the period 
ending December, 1920, for statutory 
undertakings, and March 31st, 1921, in 
the case of local undertakings, and were 
thus compiled before any material pro- 
gress with the method of charging by 
therms had been made. The figures for 
the subsequent year will, therefore, be 
awaited with interest. 




A booklet issued bj Electrical Installa- 
tions, Ltd., under the above title rightly 
lays stress on the fact that it is not 
enough merely to supply lamps and fit- 
tings. One must also provide " service " 
— that is, advise consumers as to the best 
method of using the goods supplied. 
This applies to all lighting problems, but 

electricity. We should like to see these 
facts emphasised by all contractor-. 

The booklet contains a varied assort- 
ment of photographs of lighting installa- 
tions in all kinds of premises, repair 
shops, motor stores, paper mills, etc., 
offices, country houses, etc. One of the 
most plea-sing views, taken by artificial 
light, is that reproduced below — the 
entrance ball of the offices of Messrs 

The Entrance Hall of the offices of .Messrs. Mailer & Co., Ltd, Holland House. An 
example of Decorative Lighting. 

it is perhaps Bpecially necessary in tin- 
case of industrial lighting, owing to the 
varied demands of different kinds of 

A leaflet issued by the same firm points 
<.ut the advantages of efficient shading 
in reducing strain on the eyes and the 
need for careful arrangement of the 
lighting units to obtain even illumination. 
By substituting up-to-date appliances 
for obsolete fittings it is often possible 
to obtain these advantages and yet to 
make economies in consumption of 

Wm. Miiller & Co.. Ltd.. at Holland 

We understand that the building is 
decorated in a distinctive Dutch style 
throughout and that much of the 
lighting is of a highly ornamental 

Special installations of this type are 
always interesting to record, and suet ■« — 
in carrying out ornamental scbemes of 
lighting depends very greatly on efficient 
work and intelligent interpretation of 
requirements by the contractor. 



illuminating Engineering Society. 

(Pounded in London, 1909.) 


Tel. No. Victoria 5215. 


Illuminating Engineering and Architecture. 

On the occasion of the joint discussion of the Illuminating Engineering 
Society and the Royal Institute of British Architects on " The Lighting 
of Public Buildings," on March 28th, we gave expression to the general 
desire for closer co-operation between the architect and the illuminating 
engineer, who have much to gain by interchange of views on lighting. 
We are glad to notice that a summary of the introductory paper read at 
this meeting by Dr. E. H. Rayner, Mr." J. W. T. Walsh and Mr. H. Buckley 
of the National Physical Laboratory, has since appeared in the official 
journal of the R.I.B.A. Another opportunity of inviting the co-operation 
of architects was afforded by the recent paper on " Illuminating Engineering 
in relation to the Architect," read by Mr. L. M. Tye before the Royal 
Institute of British Architects on November 10th. 

From the very inception of the il uminating engineering movement, 
the important relation of the architect to various fields of lighting has 
been realised, and it may be recalled that in the very first volume of The 
Illuminating Engineer a special section was devoted to this matter. 
The developments in lamps and lighting appliances that have since taken 
place only serve to render co-operation more desirable. There is now such 
a variety of lamps and fittings available that architects can obtain 
practically any desired result by consultation with lighting experts who 


are conversant with all the latest lighting devices. In deciding the methods 
of lighting in buildings of historic interest and architectural distinction 
such concerted action is particularly necessary. The lighting of many 
such important buildings naturally rests largely in the hands of the 
architect responsible for their design. In some cases, notably the new- 
Port of London Building, described by Capt. W. J. Liberty recently 
before the Illuminating Engineering Society, he has left the impress of 
his personality on the illumination. But there are doubtless other build- 
ings where better lighting effects could have been obtained if the illumina- 
tion had been more closely studied, and the contractor taken into the 
confidence of the architect at an earlier stage in the design. If the scheme 
of artificial illumination and the corresponding expenditure are left until 
the building is practically complete, this naturally makes the provision of 
suitable lighting more costly and difficult. 

Such difficulties should not arise when the architect and the lighting 
expert confer at an early stage in the planning of the building, the former 
giving a clear indication of the effects he desires to produce, and the latter 
furnishing suggestions as to how these intentions can best be realised. 
The planning of access of daylight has long been an important element 
in the architects' designs But in the present age ought not equal 
attention to be given to the provision of adequate artificial illumination ? 
Interiors are now used by artificial light to a far greater extent than in 
the past. In some cases theatres and cinema halls for example- 
artificial lighting may be said to be the dominant consideration: But 
apart from such special cases the appearance of distinctive and beautiful 
interiors by artificial light is now a matter of direct concern to the architect, 
who naturally desires his work to be appreciated by night as well as by 
day. In the case of such buildings as churches, public libraries and 
offices, museums, etc., concerted action on the part of architects and lighting 
experts, which in some instances has already yielded useful results, is 
much to be desired. 

Exterior lighting, again, offers many opportunities for the exercise 
of the architect's influence. Apart from its primary aim of assisting safe 
and speedy traffic, public lighting in thoroughfares should be so contrived 
as to show up the exteriors of important buildings. The flood lighting of 
external features of buildings is one new field where the judgment of 
architects would be invaluable ; it would likewise be useful in designing 
the facades of large stores, where provision for exterior lighting effects 
should form an essential part of the design. 

In view of these facts the writer suggested, at the meeting of the 
R.I.B.A. mentioned above, that courses of instruction on illumination 
should be embodied in the curriculum for architectural students. It is 
somewhat singular that in a recently issued and otherwise admirable hand- 
book for those entering the architectural profession, no reference is made 
to artificial lighting, and no books dealing with the subject are mentioned. 
It is equally important that those dealing with the technical aspects of 
lighting should be aware of the considerations that guide architects in 
.the planning of artificial lighting. Courses of lectures for engineering 
students dealing with illumination should therefore contain at least a 
few lectures dealing with this aspect of the subject, and similarly courses 
of instruction for students entering the architectural profession should 
include some lectures specifically devoted to technical aspects of 


The Eleventh Annual Conference of the British Commercial Gas Association. 

On pp. 27(1-278 in this issue we give an account of the proceedings 
at the Eleventh Annual Conference of the British Commerical Gas Associa- 
tion, which took place in Bristol during October i6th-i8th. One of the 
guiding principles emphasised in the Presidential Address of Sir George 
E. Davies, and in the various papers presented, was the necessity for 
recognition on the part of a gas company that it is out not merely to sell 
gas but to do useful public service. Accordingly every effort should be 
made to gain the confidence of the consumer and show how to make the 
best use of modern gas appliances. For this purpose periodical popular 
lectures and demonstrations, or small exhibitions such as the gas-lighted 
bungalow at Croydon mentioned in our last issue, are very valuable. It 
is, however, important that members of the staff presiding or demonstrating 
on such occasions should be thoroughly familiar with the latest advances 
in illuminating, engineering and we hope that gas companies throughout 
the kingdom will follow the example of some of the leading undertakings 
by making some members of their staff members of the Illuminating 
Engineering Society. 

Another interesting point was the reference in the address on " Light 
and Life," delivered by Sir Henry Gauvain, to the important part played 
by sunlight in the treatment of rickets among children aptly described 
as one of the " diseases of darkness." The importance of abundant sun- 
light is now much better appreciated by the medical profession than in 
the past. We have little doubt that many other instances of its beneficent 
action will be discovered in the future, and that a direct relation between 
conditions of artificial light and health will also be found to exist. 

The most important paper, from the illuminating engineering stand- 
point, was that read by Mr. Robert Watson of Doncaster on industrial 
lighting. Mr. Watson, after tracing recent developments in gas lighting, 
devoted a considerable part of his address to the contents of recent reports 
of the Home Office Departmental Committee on Lighting in Factories and 
Workshops. He showed how the requirements could be quite easily 
fulfilled by the aid of modern gaslighting appliances and pointed out that 
the recommendations should be readily accepted as being made in the 
interests of workers and employers alike. Seeing that gas is used so largely 
as a heating agent in various industrial processes, industrial lighting pre- 
sents a very favourable field for gas. It is important that the recommenda- 
tions of the Home Office Committee should be widely understood and 
Mr. Watson has done a useful service in bringing the matter before the 
gas industry. We anticipate that these requirements will be dealt with 
in a number of papers before scientific societies and trade associations 
in the near future, and we have reason to believe that judicious publicity 
of this kind will be much appreciated in official quarters. 

A 2 


The British Empire Exhibition. 

From the accounts we have received it appear that good progress 
is being made towards the organisation of the British Empire Exhibition, 
which is to be held at Wembley Park during the period April— November 
1924. The exhibits are expected to cover a wide field, and the exhibition 
promises to be one of the most important of its kind. An exceptionally 
good opportunity is therefore presented of dealing with illumination on 
enterprising and scientific lines. 

We observe that in Group XXXII., devoted to lighting, heating and 
ventilation, arrangements are made for the inclusion of lamps and fittings 
(for use with gas, electricity and other systems of lighting) and photo- 
metric apparatus. Technical committees have been appointed to deal 
with various other groups of scientific exhibits and doubtless a similar 
course will be followed in the case of illumination — a field in which the 
co-operation of those prominently identified with the subject is particularly 
desirable. Lighting exhibits require special care. The mere display of lamps 
and fittings is in itself of comparatively small value. They may be seen 
any day in the showrooms of any leading firm. What is needed is a care- 
fully supervised series of practical illustrations of the application of artificial 
light for purposes of illumination, supplemented by popular lectures — some- 
thing new and of outstanding interest that will serve to mark a novel 
departure, and illustrate the development of illuminating engineering 
during the past 14 years. 

The lighting of the Exhibition will presumably be the subject of special 
study by a competent committee, and this in itself should be an exhibit 
of exceptional interest. In the discussion before the Illuminating Engineer- 
ing Society on " Light as an aid to Publicity " last year, there was a general 
recognition that the lighting of exhibitions in this country in the past had 
been far from satisfactory. In many cases there was no ordered plan. 
Each exhibitor was a law unto himself, with the result that some stalls 
were inadequately lighted and others glaring and crudely brilliant, dis- 
tracting attention from neighbouring exhibits. In addition little in- 
genuity was shown in the general lighting of such exhibitions. 

The remarkable shop-window, proposed for the British Empire Ex- 
hibition, with a frontage of 3,500 feet, a depth of 200 feet, and an area 
of 9,000,000 square feet, presents a unique opportunity for novel and 
effective lighting on a uniform plan. 

Lighting conditions at some exhibitions in the past compared poorly 
with the unique spectacular lighting designed for the Panama-Pacific 
Exhibition opened in San Francisco just before the war. We gather that 
similar arrangements were made for the Brazilian Centennial Exposition 
that was opened in Rio de Janeiro last September to commemorate the 
one hundredth anniversary of the independence of the ignited States of 

Light is in these days intimately associated with Publicity. The 
organisers of the British Empire Exhibition have a great opportunity 
of devising appropriate special illumination, and there is as yet plenty 
of time to make preparations. No doubt they will grasp this opportunity 
of showing that this country can do equally well what has been done 

Leon Gaster. 




By Loyd A. Joxes. 
(Continued from p. 254 September issue.) 

In the first section of this paper the 
basis of comparison of the photographic 
efficiency of illnminants was discussed 
and some figures for typical sources of 
light used in kinema studios were given. 
The next question that requires con- 
sideration in a complete discussion of 
this subject is the relation between 
brightness of the object photographed 
and the illumination on the photographic 
plate where the image is received. 

Transmission of Photographic Lenses. 

Lenses are commonly composed of a 
number of components and some light 
is reflected at the boundaries of each 














Fig. 7. — Showing transmission of light by photo- 
graphic objective throughout the spectrum. 

surface, and accordingly lost. Some 
light is also lost by absorption in the glass 
lenses and in the Canada balsam used to 
cement the surfaces together in some 
lenses. The absorption of light increases 
very rapidly in the ultra-violet. This is 
illustrated in Fig. 7 which shows the spec- 
trophotometry transmission for the lens 
elements of a well-known type of photo- 
graphic objective. In the visible region 
the transmission is only 75 per cent, and 
this decreases very rapidly between 300 
and 400^/u. 

Apart from such losses the relation 
between brightness of object and illumina- 
tion incident on the photographic plate 
can be computed theoretically on strictly 
geometrical considerations. This matter 
has been studied in detail bv P. G-. Nutt- 
ing and G. W. Moffitt. 

The factor varies little with distance 
of object or focal length of lens. Hence 
taking values for a lens with a focal 
length of 50 mm. and an object at a 
distance of 25 ft. the curves shown in 
Fig. 8 are plotted. 









2 4 • 16 » 

Fig. 8.— Relation between N„/B and lens- 

The ordinate, values are of the ratio 
N x /B (theoretical) while abscissa? are 
in terms of the stop (ratio of focal length 
to diameter of lens-aperture). The or- 
dinate valnesapply to the left-hand curve, 
while for the right-hand curve they 
should be divided by ten. 

Clearly in order to connect brightness 

* Communicatii n No. 
slightly abbreviated. 

135 from the Research Laboratory of the Eastman Kodak C<>. 



of object and illumination of image we 
have to ((insider two factors: (1) the 
physical characteristics of the image 
forming system including the sources 
of absorption mentioned above, and (2) 
the geometrical characteristics of the 
system. We may denote these two 
factors by symbols Z p and Z a . Then 
Z=Z p .Z fe , is a number which satisfies 
t he equation : — 




If B„ be expressed in lamberts X will 
be in terms of photons. Z^=N«/B 
(theoretical) as already indicated in 
Fig. 8. The value of Z p has been measured 
and published for various lenses, which 
show variations in transmission of from 
053 to 067. It seems a fairly reason- 
able average value to take Z p as about 
068 for kinemat >graph Lenses. 



« n 



Fro. 9. — Relation between density and 
exposure (kine -negative film). 

Determination of Illumination for 
a Given Exposure. 

It is now possible to deduce a method 
by which the exposure necessary, with 
a given illumination, may be readily 
estimated ; or alternately the illumina- 
tion corresponding to a certain exposure 

In Fig. 9 a typical characteristic curve 
for kine-negative films is given, in Fig. 10 
a similar curve for kine-pan chromatic 
films. These two materials represent 
almost completely the types of photo- 
graphic materials used for making 
negatives for motion picture work. 

The items we are concerned with are 
as follows : — 

B„ (min.) = Brightness of the object 
in deepest shadow which 
it is desired to reproduce. 

D (min.) — Minimum density desired 
in the negative. 

Log E (min.) = Exposure indicated by 
the characteristic curve 
of the material which 
corresponds to D (min.) 

t = time of exposure. 

W v = Relative photographic 
efficiency of illuminant. 

X (min.) = Illumination on the 
negative material corres- 
ponding to object-bright- 
ness B. 

The following relations between these 
factors have been determined : — 

N\ (min.) X. B (min.) 

N\ (min.)l E x (min.) =t.B (min.) .Z 

B„ (min.) =E„ (min.) /t.Z. 




! r^ 





Ij Is 5j Xi Ia T.» ao <u o» 

Fio. 10. — Relation between density and log 
exposure (panchromatic film). 

This relation assumes that the object 
to be photographed is non-selective as 
regards radiation it receives. Also that 
there is no selective absorbing material 
between light source and object illumin- 
ated, or between object and camera. 

Furthermore, no allowance has yet been 
made for the relative photographic 
efficiency of the illuminant, sensi metric 
tests of photographic materials being 
based on exposure to sunlight (having 
a value 10 or 100 per cent.). We must 
therefore divide the right-hand side of 
the above equation by W,. as previously 



defined, thus arriving at the new re- 
lation : — 

E x (miii.) 

B (min.) 

t.Z. W v 

In like manner we may. if necessary. 
introduce another factor to allow for the 
selective reflection of the object, or the 
use of selectively transmitting screens 
either between illuminant or object or 
between object and camera. However, 
for the sake of simplicity let us assume 
that there are no such selective qualities 
to be considered. 

In practice it is usually desired to 
render the deepest shadow of the object 
by a density in the negative as low as 
possible. From Fig. 9 it is seen that 
the effective part of the curve ends at 
a density of approximately 0"2. Fol- 
lower densities the gradient of the curve 
is so low as to be of doubtful use. Hence 
a density of 0*2 should represent the 
deepest shadow of the object. The cor- 
responding log. E value is — 21, and 
of E, 00125 metre-candle-secs. Let us 
assume the use of a lens at f=3"5, having 
a transmission value (Z p ) of - 67. The 
corresponding value of N x /B (theoreti- 
cal), i.e., of ZL is 0-06. This factor con- 
verts object brightness in millilamberts 
to image illumination in phots. In 
order to convert object brightness in 
millilamberts into image illumination in 
metre-candles, the Z s must be divided by 
ten, and thus becomes 0"006. 

Let us next assume that the object is 
photographed by a nitrogen-filled tungsten 
lamp operating at 25 lumens per watt. 
The relative photographic efficiency, as 
given in Table 4, is 067. We can now 
collect data as follows : E x (min) = 
0-0125 ; t=0031 sees, (a usual value 
in practice). Z„=0 - 006 and Z p =0 - 67. 
Hence Z=Z g x Z p =0004. W, =067. 
Substituting these values in our equation 
above we have :— 

0-0 125 
B„ (min.)= . ()31 (1 . ()))(; . 67 = 

Assume that the material which forms 
the deepest shadow has a reflecting 
I tower of 0*05. The equation relating 
brightness reflecting power and illumina- 
tion is:— B=B.N./10 millilamberts. 

Hence we have N=100 x 10/0-05= 
20,000 metre-candles . 

1<M> ml. 

A final correction may be needed to 
allow for selective absorption by materials 
between light source and object or be- 
tween objeel and lens. On some points 
there are hardly sufficient quantitative 
data available for precise calculation and 
the system of units is at present some- 
what heterogeneous and unwieldy. But 
the above calculation will give a general 
idea as 'to how the various quantities 
are related. 

The Effect of Light and Radiation 

on the Eye. 
We now come to the consideration of 
possible effects on the eye of harmful 
radiation or excessive intensity or undue 
contrast. Within recent years there 
has been much discussion of the effects 
of ultra-violet and infra-red radiation. 
Roughly speaking, any radiation of wave- 
length shorter than 400/i/u is termed 
ultra-violet, that of wavelength beyond 
700ju^ is referred to as infra-red. Cataract 
has been attributed to the action of 
unduly powerful infra-red radiation and 
injuries to the retina and other parts 
of the eye have been ascribed to ultra- 
violet rays. A complete bibliography of 
the subject will be found in the Trans- 
actions "of the Illuminating Engineering 
Society (U.S.A.) for 1914 (pp. 311-331) ; 
also in the Proceedings of the American 
Academy of Arts and Science (Vol. 51, 
1916, pp. 630-817). A very complete 
treatment of the subject was also 
presented in 1921 by F. H. Verhoeff and 
Louis Bell. From the various researches 
so far undertaken, the following con- 
clusions may be drawn : — 

It is definitely established that radia- 
tion which is actually destructive in its 
action on living tissue is confined to 
wavelengths shorter than 300/u/i. Such 
radiation is almost completely absorbed 
by the cornea, crystalline lens and 
vitreous humour of the eye. and hence 
can never reach the retina in sufficient 
quantity to cause injury unless very 
intense sources are focused on the retina 
by optical systems transmitting these 
wavelengths. ' Therefore, under practical 
conditions no actual destructive action 
on the retina can take place. 

It should be pointed out that liability 
to injury is much greater with sources of 



extremely high intrinsic brilliancy than 
with extended surfaces. Possibility of 
injury may, therefore, be eliminated by 
the use of diffusing screens — a measure 
which is very desirable as a means of 
insuring safety. 

In sunlight at the earth's surface there 
is only a very small amount of radiation 
of wavelength shorter than 305/i/x 
(usually only about 0*25 per cent, of the 
tut. 1 radiation). Under normal con- 
ditions this is insufficient to cause injury. 
Yet, if the eyes arc exposed to Bnowfields 
illuminated by brilliant sunshine, snow- 
blindnes3, involving actual injury to the 
retinal tissue, may be caused. We may 
conclude that with the light sources used 
in the illumination of kinema studios 
there is little danger of injury to the 
retina if ordinary precautions, such as 
the use of diffusing screens and glass 
globes, are taken. 

The absorption of ultra-violet light by 
the cornea and crystalline lens may 
occasion temporary but painful injuries, 
but evidence suggests thai recovery is 
complete and no permanent damage 
results. However, the energy-density 
necessary to produce such injuries is 
very high, and with proper precautions 
no danger should exist. No injuries 
arising from radiation of wavelength 
between 305^/u and 400^/u have been 
definitely observed. 

It is, however, very clear!) established 
that certain conditions of illumination 
produce unnecessary strain, fatigue and 
discomfort. These effects may be pro- 
duced by the use of intensities and con- 
trasts too great to be met by the processes 
of adaptation in the eye. The require- 
ments of the eye have been closely studied 
by Nutting, Blanchard, Reeves, Fence 
and Rand, and others. The eye operates 
over a range of intensity of approximately 
1 to 10 billion. The most efficient range 
of operation is that lying between the 
brightness-level represented by average 
daylight and that of well-lighted interiors 
by night. The efficiency of the eye falls 
off rapidly for brightnesses exceeding 
r lambert and slowly for brightnesses 
below 1 millilambert. It can, however, 
withstand considerable overloads for short 
periods. The functions of the retina of 
importance in determining efficiency and 
visual comfort are represented graphically 

in Fig. 11. These curves illustrate the 
sensibility of the eye to glare, contrast 
and brightness. The impression received 
depends on the state of sensibility of the 
eve at the moment of stimulus, and the 
abscissa values in Fig. 11 assume certain 
levels of adaptation, plotted, for the 
sake of convenience, as logarithms of 
a (tual numbers. The figures enable us 
to determine the brightness which is just 
uncomfortable (glare), the just perceptible 
brightness (threshold), and the difference 
in brightness which can just be perceived 
(discrimination). It will be noted, for 
example, that, for an adaptation level 
(field brightness) of 1<H) ml., a brightness 
of 7 - 2o lamberts is required to produce 
glare. Under such conditions any light 
Bource or reflecting or diffusing material 
having a brightness exceeding 7 lamberts 
(approx. "_' "2 candles per Bq. cm.) would 
cause discomfort. This is far below the 
intrinsic brilliancy of light sources used 
in modern illumination, which must. 
therefore, be removed from the held of 
vision or used with some form of diffusing 
screen between source and observe]-. 

The elimination of glare in kinema 
studios is of great importance. It is 
undoubtedly true that long-continued 
exposure to extremely high intensities 
and contrasts produce fatigue which 
may in time result in permanent injury. 
Moreover, from the standpoint of good 
acting, glare is most undesirable, for an 
a<tor cannot effectively register the 
desired emotions when in a state of 
extreme discomfort. It is improbable 
that the adaptation level in kinema 
studios is greater than 10 lamberts, and 
on this assumption no area having a 
brightness of 30 lamberts (approx. 10 
candles per sq. in.) should be tolerated 
in the field of view. This value is again 
far below the intrinsic brilliancy of most 
light sources. 

Glare from lighting sources can usually 
be avoided by placing the source high, 
by concealing the source (as in indirect 
or semi-indirect lighting) or by using 
diffusing globes over the source. Any 
want of uniformity in the brightness of 
various parts of the field of view is also 
liable to cause glare, and vision is best 
with contrasts not exceeding about ten 
to one. 

There are two extremes in problems of 



illumination, first to tolerate any system 
that does not cause permanent injury, 
second to reject any system which causes 
even the slightest ocular discomfort. 
While it may not be practicable to 
relieve the eye from all possible strain, 
it would be well to aim at better lighting 
conditions than prevail at present. The 
eye is capable of withstanding some 
overload, but it should not be abused. 
After taking all precautions to eliminate 
glare from sources of light, there may 
still remain objects in the field of view 
capable of creating an impression of 

effects due to harmful radiation there is 
usually a latent period before discomfort 
begins. The first experience is usually 
an impression of having " sand in the 
eves." Then comes sharp pain in the 
eyes, which may finally spread to other 
parts of the face. In cases of instan- 
taneous glare, discomfort may be caused 
by the strain on the ciliary pupil muscle 
in contracting the pupil. In fact, much 
eye trouble is due to fatigue of some or 
all of the ocular muscles. Many people 
should wear glasses who do not .realise 
the fact. Some defects are emphasised 

-J -t -3 -e -/ c / z 

Fig. 11. — Illustrating the sensibility of the eye to glare, contrast and brightness. 

glare. Polished and glazed surfaces in 
which reflections of light-sources appear 
should be eliminated so far as possible. 
In cases where very intense illumination 
and undesirably high contrasts are judged 
to be absolutely necessary for producing 
certain effects the strain on the eyes 
might be relieved by only using this 
form of lighting when the scene is 
being actually recorded, and not during 

Though in practice no cases of struc- 
tural changes have been recorded, the 
injurious effects of improper lighting 
methods show themselves by interference 
with ocular symptoms. As in the case of 

by certain conditions of illumination and 
some forms of trouble met with in the 
kinema-industry are doubtless due to 
personal defects of vision. 

From the standpoint of vision, the 
most " efficient " illumination is that 
which permits the eye to function with 
the least strain and effort. Good lighting 
facilitates good seeing. The comfort of 
out-of-door daylight conditions should 
he the standard. It is possible, when 
necessary, to obtain a suitable proportion 
of direct and indirect light. In all cases 
the eyes should be considered and the 
physical laws involved should be sup- 
plemented by " psychophysics." 




Eleventh Annual Conference at Bristol, Oct. I6th I8th, 1922. 

Ai the Kleventh Annual Congress of 
the British Commercial Gas Association, 
held in Bristol during October 16th — 
18th, there were many references to 
illumination. After the Lord Mayor 
had welcomed the members of the 
Association and the President (Alderman 
Sir George E. Davies, .J. P.) had briefly 
responded, a lecture on " Light and 
Life " was delivered by Sir Henry 
Gauvain, M.D., M.R.C.S., L.R.C.P., who 
had been medical superintendent of the 
Lord Mayor Treloar ( ripples' Homes at 
Alton (Hants) and at Hayling Island 
since 1904. 

Light and Life. 

Sir Henry, in opening his lecture, 
remarked that the public were becoming 
more and more acquainted with matters 
relating to public health. Light therapy 
had been practised at Alton since the 
hospital was started. But the summer 
of 1921, with its glorious sunshine, and 
the contrasting wet summer of 1*. 22, had 
drawn public attention to the part 
played by light as an indispensable factor 
in our daily lives. Much research had 
been done on the action of light in the 
prevention of disease. Rickets, for in- 
stance, had been described as a " disease 
of darkness." It was formerly thought 
that poor diet was the determining factor. 
Many children in the large towns of this 
country contracted the disease. In some 
great cities in India the children of very 
poor people, who lived on an inferior 
diet but constantly played in the open 
air, did not get rickets. Yet in these 
same cities the children of wealthy 
Hindoos, who lived a secluded life and 
were very carefully tended, did acquire 
the disease. 

Other instances of the curative effect 
of light, notably as a destroyer of the 
tubercle bacilli, were mentioned and the 
lecturer ascribed much of the wonderful 
results obtained at Alton and Hayling 
Island to the beneficial influence of 
abundant sunlight. In conclusion, Sir 
Henry referred to the fact that we, who 

were in many respects one of the most 
hygienic peoples, were content to tolerate 
the vitiation of air by smoke, and urged 
that the gas industry should continue to 
use its influence in favour of smoke- 
abatement. He also suggested that the 
Association should investigate the use 
of gas lighting for therapeutic work, 
and the possibility of obtaining with 
artificial light some of the beneficial 
results of exposure to sunlight. 

Presidential Address. 

After the subsequent business meeting. 
Sir George E. Davies delivered his 
Presidential Address, in the course of 
which he said that members of the gas 
industry should regard themselves as 
doing public service, and should be 
prepared to educate the consumer. The 
publicity work of the B.C.G.A. was of 
very great value and the publication of 
the " Teachers' Notes of Lessons on 
the Manufacture, Distribution and Use 
of Gas " had been a notable step. The 
few accidents that occurred, due to the 
misuse of gas, could be still further 
diminished by educational work. The 
training of employees was likewise an 
impoitant duty. 

Sir George then proceeded to refer at 
length to the Gas Regulation Act, and 
the method of charging by " therms 
regarding which there had been so much 
discussion in the press. He ascribed 
the outcry of " big gas bills " to three 
chief causes : (1) the exceptionally cold 
and dark spring and summer this year, 
as compared with 1921, (2) the three 
months' national coal-stoppage in 1921, 
when everyone economised in fuel of 
every description, and (3) the fact that 
the present year is the first one since 
1914 when consumers have been able to 
get unrestricted supplies of gas. 

The Gas Industry as a Public Service. 

The series of papers read at the con- 
ference on the above subject all empha- 
sised the need for recognition that gas 



companies were entrusted with a public 
service. Mr. S. E. Halliwell, in a paper 
on " The Consumer's Point of View," 
laid special stress on a courteous attitude 
in approaching the consumer, complete 
maintenance schemes on liberal lines, 
and efforts to educate the public in the 
use of the most efficient gas appliances. 
Mr. W. N. Westlake, dealing with "Gas 
as a Domestic Servant,'" explained, by 
the aid of illustrations, modern methods 
of gas heating and cooking, etc., dwelling 
on the merits of gas in countering the 
smoke problem. Mr. P. S. Hoyte de- 
scribed some " All Gas Houses " and 
Mr. P. G. G. Moon lectured on "Gas 
Service in Seaside and other Health 
Resorts."' All these papers were at- 
tractively illustrated. 

Gas as a Service to Industry. 

In this section there were two papers 
by Mr. W. M. Mason and Mr. Robert 
Watson respectively. Mr. W. M. Mason, 
in discussing " Gaseous Fuel and 
Power in Industry," described the appli- 
cations of gas in a variety of industrial 
processes, giving, in an appendix, an 
alphabetically arranged survey of a 
large number of trades and industries 
and mentioning the cases in which gas 
had been found specially useful. 

Mr. Robert Watson's paper, of which 
we give a summary, was devoted to 
industrial lighting. 

Modern Gas Lighting with special 
Reference to the Illumination of 
Factories and Workshops. 

Mr. Watson, in the introductory por- 
tion of his paper on the above subject, 
briefly 'traced the recent developments 
in gas lighting since 1885, referring 
mainly to the introduction of the in- 
verted mantle, the development of 
superheated gas burners, and high 
pressure gas lighting. He pointed out 
that by aid of the superheated burner 
as much as 30 candles per cub. ft. could 
be obtained under ordinary pressure ; 
in some of the most recent cluster types 
as much as 40-50 candles per cub. ft. 
had been claimed, and up to 1,000 c.p. 
had been obtained from units of this 
type. With high pressure a lighting 

value of 60 candles per cub. ft. or more 
was possible, and the units available 
ranged from 100, 150 and 300 c.p. in 
factories up to as much as 4,500 c.p. 
for large open spaces. 

Attention was drawn to the physio- 
logical importance of good lighting, the 
lecturer remarking that good and ade- 
quate illumination was now regarded as 
a necessary requirement of civilised life 
and an essential in business and industrial 
work. The importance of the subject 
was illustrated by the attention devoted 
to it by Government Departments. 
Although statutory enactments might at 
times cause perturbation, they should 
be welcomed as acting in the direct in- 
terests of employers and workers. 
Lighting experts had been able, by prac- 
tical experience, to crystallise views on 
safe and adequate lighting, and it might 
be useful to summarise these principles 
as an indication of the probable statu- 
tory requirements of the future. 

Mr. Watson then gave a brief account 
of the recommendations made in recent 
reports of the Home Office Departmental 
Committee on Lighting in Factories and 
Workshops in this country. The survey 
was brought up to date by a reference 
to the most recent reports, dealing 
particularly with the recommendations 
for the avoidance of glare and the values 
of illumination for fine and very fine 
work, put forward not as legal minima 
but as an indication of " recommended 

The code of factory lighting framed 
by the American Illuminating En- 
gineering Society was next discussed. 
Attention was drawn to the fact that 
the general standard of illumination has 
risen and is still rising in progressive 
factories. Some figures published by 
Mr. A. E. Broadberry were quoted as 
illustrating values usual with good 
modern practice. Reference was made 
to various records of improved output 
following the introduction of better 
lighting. The cost of lighting was 
usually only a small fraction of the wages 
bill and there were many cases where 
improved illumination could be obtained 
without expense, simply by the adoption 
of modern and suitable fittings. It was 
certain that the requirements and sug- 
gestions in the reports on industrial 



lighting were well worth consideration. 
Time and again it had been said, and it 
was well known, that gloomy surround- 
ings caused depression and that work 
was better and more cheerfully done 
in factories and rooms where the illumin- 
ation was satisfactory. Good lighting 
undoubtedly paid from every point of 
view and money invested in a rational 
and improved scheme of illumination 
might be regarded as a profitable in- 

Turning next to some fundamental 
principles of good Lighting, Mr. Watson 
emphasised the desirability of avoiding 
extreme variations and troublesome 
shadows such as subjected the eye to 
sudden changes. In particular steadi- 
ness of light and avoidance of glare 
should be aimed at. The necessity for 
local lighting was less than in the past 
as excellent general illumination could 
now be provided. Local lighting was 
still desirable for certain forms of work, 
but should be regarded as supplementary 
to the genera] illumination. All re- 
quirements in these respects could be 
met with modern gas-lighting appliai i es. 

After discussing the characteristics of 
direct and indirect lighting, Mr. Watson 
pointed out that semi-indirect methods 
(which combined the advantages of both 
these systems) could he readily adopted 
with gas, clusters of burners being 
mounted in translucent howls. It was 
remarked that the ordinary incandescent 
mantle with an intrinsic brilliancy of about 
25 candles pel square inch still ranked 
low in comparison with the brightness of 
some other sources. Nevertheless even 
25 candles per sip are inch might be too 
high fordirect vision. About 5 candles pec 
square inch was regarded as the maxi- 
mum advisable where the eye directly 
encounters light rays, and with propel 
diffusing globes this value could be 
readily obtained. For purposes of shad- 
ing the heat-resisting glassware of the 
vitreosil or silica glass type was par- 
ticularly useful. 

In the final portion of his address Mr. 
Watson referred to the valuable quality 
of gas lighting in promoting ventilation, 
and to the convenient methods of distant 
control now available. Modern gas light- 
ing could provide all that was necessary 
to satisfy statutory requirements. 


We notice that Mr. Ernest Morison, in 
an address to the Publicitv Club on 
October 30th, remarked that, so far as 
Britain is concerned, advertising by 
illuminated siiiiis could be traced back 
as far as the year 1855, when a Mr. 
Anderson obtained the first patent for 
advertisements, painted on canvas wind- 
ing round a roller and lighted with gas 
at the back. The method has, of 
course, since been applied with electric 

Moving colours and colour-combina- 
tions were apparently first suggested in 
1876. Electric signs proper were used on 
the Grand Hotel. Trafalgar Square, and 
the Gaiety Theatre in 1882, and in the 
following year football matches were 
played by the electric light in Hull. 

A notable development was the scheme 
of a man named Douglas in 1889, who 
first arranged to let out spaces on signs, 
chiefly in railway stations. As early as 
1889 exception was taken to the un- 
sightly nature of some electric siL;ns. 
a petition being presented to the L.C.C. 
against the disfigurement of "the finest 
site in Europe (Trafalgar Square). The 
first thermal flasher was brought out in 
1904. In 19KI the first step was taken 
towards co-operative electric advertising 
by the electrical supply companies — a 
scheme since replaced by the activities 
of the E.D.A. From that year onwards 
developments have been rapid and many 
ingenious devices have been introduced. 


The Journal of the Society of Glass 
Technology for October contains a note 
on the above subject which has also been 
discussed in the Journal of the Royal 
Institute of British Architects. Such 
decay ought not to be described as 
disease,"' for it cannot be communicated 
from one specimen of glass to another. 
It is due to lack of durability arising from 
excess of alkali. Whereas some of the 
ulass in York Minster has become pitted 
and badly corroded, the 13th Century 
glass in Westminster Abbey is still in a 
perfect state of preservation. Typical 
compositions of Roman and mediaeval 
sdass are uiven. 





Held at Swampscott, Mass., Sept. 25th-28th, 1922. 

Ix the recent issues of this journal 
reference has been made to the papers 
read before the Convention, a list of 
which appeared in our August issue 
(p. 228), while in our September issue 
(p. 241) some information given in the 
usual ** Report of Progress " was pre- 
sented. Attention was drawn to the 
progress being made in public lighting 
in the United States, decorative units 
being installed in many cities. 

In the most recent issue of the Trans- 
actions of the Illuminating Engineering 
Society (U.S.A.) and in various Ameri- 
can technical journals, further particulars 
of the proceedings presented at the 
Convention are now available, and in what 
follows we give a summary of some of 
the leading papers. Dr. Elihu Thomson, 
in his address of welcome, traced the 
development of illumination from the 
days of oil lamps up to the present time, 
and alluded to the future possibility of a 
""cold light" based on phosphorescence. 
Reports were presented dealing with 
" Nomenclature and Standards " and 
'" Glare." Amongst the problems sug- 
gested for further consideration were : 
(1) a quantitative study of " veiling- 
glare " and the degree to which this 
interferes with comfort of vision, (2) a 
determination of the region of the eye 
in which " dazzle glare " arises and of 
the extension of the dazzle area with 
increasing illumination, and (3) a study 
of light sources of considerable area and 
their effect in reducing dazzle glare, but 
lowering retinal sensibility. An account 
was also presented of the activities of 
the Committee on Education, which has 
been responsible for numerous popular 
lectures before clubs and societies and 
for various suggestions for research. 

A Survey of Residexce Lightixg. 

Two papers on this subject were pre- 
sented by Mr. M. Luckiesh and Mr. 
X. D. MacDonald. The papers were 

fully illustrated by diagrams showing 
the frequency with which various forn:s 
of fittings were used, and the geneial 
standard of equipment. Mr. Luckiesh 
finds that rented homes are less well 
equipped than homes owned by the 
householder. Poor arrangements were 
often made for shading. From 7-21 per 
cent, of ceiling fixtures and from 12-38 
per cent, of wall brackets had no shades. 
Whereas ceiling fittings are very generally 
used, wall brackets are less plentiful 
than they should be, and there are in- 
sufficient outlets. The total consump- 
tion of homes is about half what it 
should be to give adequate lighting. 

Mr. MacDonald also comments on the 
insufficiency of outlets, leading to the 
common method of plugging into one 
holder of a ceiling fitting in order to 
supply a portable lamp. Apparently 
about 25 per cent, of consumers make 
use of supplementary devices of this 
kind. About 25 per cent, of lamps are 
so situated as to be replaced with in- 
convenience and 50 per cent, of lamps 
in such positions that bare lamps fall 
within the direct range of vision. The 
two papers show how much remains 
to be done in educating middle class 
consumers in proper methods of domestic 


Mr. W. H. Rademacher dealt with 
lighting in a variety of industries con- 
cerned with the production of food, 
including grain elevators and flour mills. 
bakeries, canning, meat packing, the 
manufacture of confectionery, etc. 
Generally speaking, inadequate lighting 
exists in a high percentage of installa- 
tions visited and the standards of illum- 
ination are too low. The great value of 
good lighting in the interests of cleanli- 
ness, avoidance of spoiled material and 
efficient production is not sufficiently 



realised. In grain elevators attention is 
drawn to the value of vapour-proof 
lamps as a precaution against fire. Only 
Id pei cent, of plants inspected were 
partially provided with such units. The 
usual illumination is of the order of 0'25 
to 1 foot-candle, which is considered too 
low : 1-3 foot-candles is suggested as a 
minimum, in most parts of the works, 
hut on the machinery floor and in cars 
and shipholds 3-4 foot-candles is recom- 
mended. In flour mills higher values 
are considered necessary. Thus for clean- 
ing, grinding, rolling and separating, 3-6 
foot-candles' general illumination is desir- 
able : for bagging and weighing 6-8 foot- 
candles. For grading, on the other hand, 
local lighting giving 10-20 loot-candles is 
desirable. In bakeries, canning, ice-cream 
manufacture, 1 8 Eoot-candles is recom- 
mended for most processes. But some 
special processes, such as raisin picking 
and fruit-sorting and inspection work 
generally, need 10-15 foot-candles. The 
paper is illustrated by photographs of 
some typical good installation-, and 
methods of arranging lamps are dis- 

( Iottom Mm i. Lighting. 

Mr. J. M. Ketch's paper on this subject 
was well illustrated by photographs and 
diagrams showing positions of lights for 
various processes. Attention is drawn 
to the need for avoiding "laic, and the 
value of suitable colour-matching units 
for cotton-grading. On the average such 
values as 3'5 5'5 foot-candles seem to 
be adopted for opening, picking, raiding 
and lapping : for spinning, twisting, 
weaving, etc., a somewhat higher illum- 
ination of 5-8 foot-candles. The avoid- 
ance of troublesome shadows is a special 
difficultv, and great importance is attached 
to light surroundings. The direction 
from which light comes is very important, 
as both horizontal and vertical surfaces 
have to be well illuminated in the case 
of many machines. Great importance 
is also attached to regular cleaning of 
lamps and lighting units in mills. In 
most rooms the interval should not 
exceed seven days if units are merely 
wiped out, or ten days if units are 
thoroughly washed. In conclusion, sug- 
gestions for standardised methods of 
i ghting are made. 

The *" Drawing Power " of Shop 

Messrs. W. Sturroek and J. M. Shute, 

in a paper on show-window lighting, 
have found that increased lighting of 
show-windows in Cleveland and Newark 
led to a substantial increase in " drawing 
power." Thus when the illumination 
was increased from 15 to 40 foot-candles, 
the number of people inspecting the 
windows was increased by 33 per cent., 
while a rise to 100 foot-candles caused 
an increase of 73 per cent, in drawing 
power. The use of special coloured 
light also increased drawing power by 
18 per cent. Mr. W. DA. Ryan pre- 
dicted that in the next few years window 
illumination would average at least 100 

School Lighting. 
Professor Henry Dates summarises the 

results of an inspection of 123 schools 
in Cleveland, one typical school being 
selected as a working laboratory, in 
which various forms of lighting fittings 
could be tried. The investigation served 
as a basis for a specification for the light- 
ing of schools for the Cleveland Board. 
In some cases unsynimetrical arrange- 
ments of lights are desirable in order to 
afford sufficient light at certain spots. 
In a 28ft. 30 ft. room six units are 
usually sufficient. The researches covered 
such points as consumption per square 
foot and corresponding illuminations and 
methods of avoiding glare and promoting 
even distribution of light. 

Office Lighting. 
The study of office lighting from the 
standpoint of hygiene was undertaken 
by Dr. A. B. Emmons, of the Harvard 
Medical School Department of Hygiene. 
The co-operation of the Department was 
recently sought by 25 schools, and the 
investigation is still proceeding. Special 
attention is being devoted to daylight 
conditions. A minimum illumination of 
5 foot-candles for office work was re- 

Miscellaneous Papers. 

Among other interesting papers 

attention may be drawn to that by 

Mr. J. L. Stair on the Lighting of 

Restaurants, many highly decorative 



schemes of lighting being discussed. 
Mr. F. S. Mills, in dealing with the 
Lighting of Picture Studios, describes 
how various special effects can be pro- 
duced with the aid of varied lighting 
appliances, such sources as the high 
intensity arc lamp, the Cooper-Hewitt 
mercury vapour lamp and the high 
candlepower gasfilled lamps all having 
special applications. Mr. S. G. Hibben 
has dealt with Lighthouses, presenting 
data on visibility under varying con- 
ditions, describing many special designs 
and analysing the requirements for 
different classes of service. An interest- 
ing point raised by Mr. A. Smirnoff is 
the point of " psychological darkness " 
at which consumers begin to turn on 
lamps at a surprisingly rapid rate. 
This is stated to be in the neighbour- 
hood of about 1,500 foot-candles in the 
open air. Automatic devices installed 
at " strategic points " enable records 
of intensity of light to be obtained, and 
thus a warning conveyed of the expected 
rise in load. 


Finally, there are numerous papers 
dealing with various aspects of photo- 
metry. One of the most important 
appears to be that by Mr. F. A. Benford 
discussing the plotting of spectrophoto- 
metric data and summarising the various 
methods in use at the present time. 
There is a need for standardisation of 
method, especially as regards the method 
of plotting energy and light and the 
selection of the " point of equality." 
Other papers deal with direct reading 
scales for use with sphere photometers and 
the possible substitution of a " regular 
icosahedron " for the integrating sphere. 
Messrs. Colby and Doolittle describe 
a distribution photometer of new design 
and Prof. C. E. Ferree and Miss Gertrude 
Rand contribute an analysis of flicker 
and equality of brightness in photometers. 
It appears to be that the two methods 
give the same' result if the eye is exposed 
for the same length of time in both cases. 

Only a few of the numerous papers 
read at the Convention have as yet 
appeared in the Transactions of the 
Illuminating Engineering Society 

(U.S.A.), but the above survey will 
give an idea of their contents. 


Arrangements are proceeding for the 
British Empire Exhibition to be held in 
Wembley Park during April to October, 
1924. It is stated that the total floor 
area of the Machinery Hall and Industrial 
Hall together amounts to 884,000 sq. ft., 
and space for exhibits will be made early 
in next year. The exhibition is to be 
divided into 45 sections covering a very 
wide field, and a number of technical 
committees are being appointed to con- 
sider the various groups of exhibits. 
We understand that Sir Napier Shaw 
is Chairman and Sir Joseph Petavel, 
Deputy-Chairman of the Instruments 

In Group XXXII., devoted to Light- 
ing, Heating and Ventilation, we notice 
that two sections, relating respectively 
to electric lighting and other methods of 
illumination, are included, and there are 
other sections, such as those dealing 
with kinematography and optical instru- 
ments, which are of interest to the 
illuminating engineer. The assistance of 
various societies and associations is being 
sought in connection with the organisa- 
tion of exhibits in certain special sections. 


For Amsterdam as a city, and its Gas 
Department, 1923 promises to be an 
exceptional year, marking both the 25th 
anniversary of the taking over of the 
gas works by the Municipality and the 
50 years' jubilee of the Dutch Association 
of Gas Engineers. 

It is, therefore, interesting to note 
that the opportunity has been taken to 
arrange for an International Gas Ex- 
hibition during the period October — 
November, 1923. The exhibition will 
aim at giving an idea of all. industries, 
trades and professions in which gas is 
used, and the co-operation of British 
exhibitors is welcomed. The President 
of the Exhibition Committee is Dr. L. J. 
Terneden, Manager of the Municipal Gas- 
works of Amsterdam. All correspond- 
ence should be addressed to " Het 
Secretariaat der Internationale Tentoon- 
stelling op Gasgebied, Amstel No. 1, 




During fche past year several interesting 

applications of flood lighting, in London 
and elsewhere, were recorded in this 
journal, and the application of concealed 
lighting for purposes of advertisement is 

becoming more common. A notable 
instance is afforded by several displays at 
fche junction of Charing Cross Road and 
Oxford Street. A portion of the large 
frontage of the building formerly occu- 
pied by Crosse and Blackwell is now 
covered by placards illuminated by 
lamps at top and bottom equipped 
with special trough reflectors. Although, 
owing to the fact that the sources are 
necessarily placed close to fche wall, fche 
illumination is somewhat uneven, the 
• fleet is quite striking, and the departure 
is interesting. One can foresee that in 
future the illumination of large placards 
by night will become a regular feature in 
advertising, and the greater value of the 
publicity afforded would doubtless be 
well worth the relatively small expendi- 
ture on artificial lighting. 

At the corner, where Tottenham Court 
Road joins New Oxford Street, there are 
several examples of concealed lighting. 
Amongst these may be mentioned the 
Scala advertisement, while a somewhat 
subdued but distinctly pleasing effect is 
produced by the flood-lighting of a 
coloured picture advertising " Sande- 
man's Port." The effect of the picture 
is somewhat obscured from certain 
points of view by the fact of relatively 
blight streetdamps coming within the 
line of vision, but nevertheless it " stands 
out " well and forms a striking adver- 
tisement. • 

Such legitimate methods of using light 
for purposes of advertisement should be 
encouraged. As has often been pointed 
out, concealed lighting is a valuable 
supplement to street public lighting as 
it helps to soften the contrast between 
street, lamps and the dark surroundings 
and contributes an element of diffused 
light which is valuable in exterior 


.Much attention has been recently devoted 
in this country to systems of " artificial 
daylight," i.e.. devices enabling the light 
from an artificial illuminant to be so 
corrected that the resultant light closely 
resembles average daylight. There is 
a general recognition of the need for some 
standard of '" white light '" against which 
such sources could be tested. The 
difficulty is that daylight itself varies 
widely in colour according to the period 
of the day. the time of the year and 
climatic conditions. It is therefore neces- 
sary to take the mean of a number of 
observations of daylight under specified 
conditions. According to a report re- 
cently issued by the Optical Society of 
America suggestions for such a standard 
have been made by Mr. Abbot of the 
Smithsonian Astrophysical Observatory. 
A curve of distribution of intensity 
throughout the spectrum, based on the 
mean of 40 tests of noon sunlight at 
Washington, is presented. Half of these 
determinations were made during the 
summer solstice and half during the 
winter solstice. Average noon sunlight 
thus defined corresponds roughly to a 
black body temperature of 5,000° K., but 
the distribution is not truly Planckian. 

Assuming that such a standard of 
natural daylight is adopted, the next step 
is to obtain a standard of '" artificial 
daylight ' strictly reproducible and in 
close accordance with it. The most 
accurate method is considered to be that 
of Priest, which consists in passing the 
radiation of a gasfilled tungsten lamp, 
operated at a colour-temperature of 
2,848° K. (about 15'6 lumens per watt 
for a concentrated filament lamp) through 
a pair of crossed nicol prisms between 
which is inserted a crystalline quartz 
plate 0*5 mm. thick with surfaces per- 
pendicular to the optic axis of the crystal. 
The resultant energy distribution is 
stated to agree very closely with that of 
standard average noon sunlight. 




In a recent lecture delivered at the 
Polytechnic (Regent Street, London), 
Prof. J. T. MacGregor Morris showed 
several interesting developments in appar- 
atus for the measurement of flux of light. 

Amongst these may be mentioned a 
cubical box of moderate dimensions with 
a white diffusing interior, which has been 
used with success for comparing the total 
flux of light from various lamps in place 
of the Ulbricht sphere. Apart from its 
shape the apparatus resembles the integ- 
rating sphere, measurements being made 
of the brightness of a window covered 
with opal glass, which is screened from 
direct light from the sources tested. A 
cubical box of this kind is naturally a 
much simpler piece of apparatus to make 
than a sphere, and if the accuracy 
suffices for ordinary measurements it 
forms an appliance which could be easily 
constructed at colleges and used by 
students. It is now generally recognised 
that measurements of light yielded in 
a single direction by sources of light are 
of little value as a basis of comparison, 
owing to the great variations in light- 
distribution of different illuminants. 
Simple apparatus for measurement of 
total flux of light is therefore greatly 
needed at the present time. According 
to the experience of Prof. MacGregor 
Morris the apparatus is quite accurate 
enough for the comparison of different 
types of lamps, values being repeated 
within 3 per cent. It would be interesting 
to know how far the device is suitable 
for testing the flux of light of lamps 
equipped with reflectors and giving a 
concentrated beam ; this is a severe test, 
and it has been conjectured that the 
accuracy, even of an integrating sphere, 
would be limited in these circumstances. 

A novel development of the cubical 
box is the " lumen-comparator." This 
consists of a rectangular box divided into 
two cubical portions by a central dividing 
diaphragm which also cuts the observa- 
tion window in two. Whereas, in using 
a simple cubical box. one must insert in 
succession the lamps to he compared, in 
the " lumen-comparator ", the lamps are 
placed simultaneously in the two divisions 
of the rectangular box. One has merely 

to measure the brightness of the two 

sections of the window as a basis of 

Prof. MacGregor Morris also showed 
the Forrest arc standard of light in 
operation. This apparatus, which has 
already been described in this journal,* 
utilises a Y-shaped arrangement of 
carbons and is based on the discovery 
that under suitable conditions the candle- 
power of the arc is directly proportional 
to the current, being 232 candles per 
ampere. This also has given most promis- 
ing results and it seems possible that 
further experiments would result in the 
evolution of a useful standard of light on 
this principle. 


It will he recalled that in a recent issue 
of this Journal" reference was made to 
some experiments on the night-lighting 
of the Croydon Aerodrome. We observe 
that a new form of combined lighthouse 
and landing light has recently been 
introduced by Messrs. Marbier, Benard & 
Turenne. This has interesting features. 

The apparatus utilises a 21-element 
dioptric lens covering 180° and lighted 
by a 13() amp. (in v. d.c. arc. which is 
mounted, on a four-wheel truck. The 
usual Venetian shutter is provided for 
flashing arrangements. In order that 
the light may be visible to aircraft the 
top of the lantern carries a supplementary 
lens built up of six elements and sub- 
tending 360 . This houses a 500 watt 
gasfilled lamp, and is stated to be visible 
it a distance of 60 miles in normal 
weather. This upper light may also lie 
used as a flashing signal, or shut off if 

When the apparatus is used as a 
landing light the shutters are left open 
ami the beam is slightly tilted, the 
lantern being installed at a height of 
54 feit above Hie ground, in these 
circumstances it is stated that an area 
ot about 7ol> yards r- dins can be effectively 
illuminated and that no direct light is 
visible to the pilot until his head is level 
with the top of the lantern. 

* Illtjm. Eng.. .Ian. 1921, p. 18. 




Progress in the past Forty Years. 

The present voir is noteworthy as being 
the loth anniversary of Edison's dis- 
covery of the electric incandescent lamp, 

so closely paralleled by Swan's researches 
in this country. The Electrical World. 
which recently issued a special issue to 
commemorate the event, draws attention 
to the remarkable progress that has been 
made in electric lighting during the 
period 1882 to 1922- far greater than 
in the previous forty years. We may 
well wonder what the next forty years 
will bring forth- whether in 1962 even 
greater changes may not have taken 

It is not generally recognised that. 
whereas the cost of most common 
commodities is much greater than it 
was forty years ago, the price of light 
is far less. .Mr. J. R. Colville contributes 
to this issue of the Electrical World, a 
.summary of developments in electric 
incandescent lamps. In L885 the 16 
candlepower carbon lamp was sold for 
one dollar (approximately Is. lid.) and 
one could obtain from the carbon lamp 
operating ai only about 98 lumen- 
hours for one cent (.'(I.). 

During the years L885 L906 the 
cost of electric energy was about halved 
and carbon filament lamps were improved 
somewhat (from 2'5 to about 4 lumens 
per watt). By 1906 it was thus possible 
to obtain 302 lumen-hours for Id. 

The coming of the tungsten lamp was a 
noteworthy advance and by the end of 
L916 tic consumer could get nearly 
1,100 lumen-hours for |d. — more than 
eleven tjmes that available in 1885. 
The introduction of tin 1 gasfilled lamp 
lias again cheapened light. At the 
present time it is reckoned that notwith- 
standing the increases, during recent 
years, in the cost of electricity, 1,138 
lumen-hours can he obtained for |d., 
so that light is now cheaper than .it any 
time during the history of electric 
incandescent lamps. 
- There has, of course, been similar 
progress in gas lighting. Tin' incan- 
descent mantle led at once to a quadruple 
increase in the amount of light obtained 
from burning a given quantity of gas, 
and subsequent advances quickly more 

than doubled this benefit. Even to-day 
improvements are still being made in 
the efficiency of burners. Much atten- 
tion is given to increases in the price of 
during the war period, but such 
advances as the latest super-heated 
inverted burners form a compensating 
element apt to be overlooked. 

Fet another consideration is the pro- 
gress that has been made in methods 
of using light. Forty years ago the 
art of shading lamps and usefully dis- 
tributing the light they yield had been 
little studied. To-day. there are avail- 
able a great variety of efficient shades 
and reflectors that enable the consumer 
to get much greater benefit from the 
illuminant than in the past. 


Under this title the Electrical World* 
comments on the recent report of the 
Home Office Departmental Committee 
on Lighting in Factories and Workshops. 
Special reference is made to the require- 
ments on glare which are considered to 
go beyond the recommendations of the 
American code and in the right direction. 
So far, it is remarked, the English Com- 
mittee has made excellent progress. Its 
ultimate conclusions will doubtless be in 
close accordance with those reached by 
the American Engineering Standards 


Ix view of the recent discussion on the 
therm as a basis of charging for gas 
a pamphlet issued by H.M. Stationery 
Office (price 4d.) makes a timely appear- 
ance. The origin and nature of the 
system are explained. An important 
feature of the recommendations of the 
Fuel Research Board is that continuous 
records should be kept of calorific value 
by the gas company, and made available 
for inspection by the consumer. Gas 
companies must declare a certain calorific, 
value. If this is altered burners in the 
households of consumers must be adjusted 
by the gas undertaking, free of charge, 
according to the heating value of the gas 

* Sept. 23. 1922. 




The firefly has long been quoted as 
the most familiar instance of a " cold 
light,'" in which only luminous rays 
and practically no heat energy are 
emitted, and it is conjectured that 
its luminous efficiency is very high. 
However, there have hitherto been 
few quantitative data in support of 
this assumption. Some measurements 
made by Dr. H. E. Ives, and recorded 
in the Journal of the Franklin Institute, 
are therefore of interest. The brightness 
of fireflies was measured by holding 
them in front of a white surface, mounted 
on a photometric bench, the illumina- 
tion being altered to secure, a balance. 
In this way the brightness was found 
to be about - 0144 lumens per sq. cm. 
This is very low compared with artificial 
illuminants — low even compared with 
the brilliancy of a typical sky (about 
1 lumen per sq. cm.). But Dr. Ives 
shows that if the ceiling of a room could 
be given a brightness equal to that of 
a firefly we should obtain an illumination 
quite sufficient for most practical pur- 
poses. If, therefore, chemists could 
produce synthetically a substance glowing 
with the same order of brightness as a 
firefly it would have useful applications. 

The next question is the distribution 
of energy in the spectrum. The energy 
is too feeble to be mapped out by 
customary methods, based on the use 
of thermo-elements, etc. But by a 
combination of spectro- photography of 
the visible spectrum with panchromatic 
plates, aided by an " extinction of 
phosphorescence " test, in the infra-red, 
Dr. Ives was able to show that apparently 
all the energy was concentrated in a 
narrow region about 056 — - 57^«, where 
the impression of luminosity is greatest. 
Hence it appears as though much, at 
least 95 per cent., of the energy radiated 
is in the most efficient luminous form. 

The total luminous efficiency, in terms 
of the ratio of output of light to energy 
consumed, is more difficult to assess, 
and the problem can only be dealt with 
indirectly. Dr. Ives makes an estimate 
based on the assumption that a man has 
an output of one watt per kg. of weight, 
whence he deduces by analogy, that a 
glow-worm expends 0"000025 watts in 

light production. This ingenious, Imt 
somewhat doubtful, calculation also leads 

to the inference that the firefly emits 
576 lumens per watt, as compared with 
the ideal of 640 lumens per watt, and 
has thus a total luminous efficiency of 
about 90 per cent. 


A useful bulletin issued under the above 
title by the Holophane Glass Co. (U.S.A.), 
which embodies recommendations made 
by members of the Illuminating Engineer- 
ing Society in the United States, deserves 
notice. After a brief summary of the 
fundamental requirements of good light- 
ing and a discussion of direct, indirect 
and semi-indirect lighting, some values 
for minimum illumination are given. 
Those for storage spaces (0"5 foot- 
candles), stairways and corridors (1 foot- 
candle) and for assembly rooms, gymna- 
siums, etc. (2 - 5 foot-candle), resemble 
values customary in this country. For 
classrooms, libraries, manual training 
rooms, etc., a minimum of 5 foot-candles, 
and for sewing and drawing 8 foot- 
candles, are recommended. 

The recommendations made in regard 
to avoidance of glare are particularly 
interesting. Thus it is specified that the 
" intensity of the brightest square inch 
of any overhead unit, visible from any 
location at which work is performed and 
located within the angle of 25° above 
eye-level, should not exceed 15 candle- 
power." It will be noted that this require- 
ment closely resembles that contained in 
the last report of the Home Office 
Departmental Committee of Lighting in 
Factories and Workshops in this country.* 

Some simple examples for the calcula- 
tion of illumination are given, based on 
the formula :— Foot-candles = Lumens X 
coeff. of utilisation X depreciation factor. 
Floor area in square feet is given. A 
useful item is a series of tables for 
coefficients of utilisation of various 
lighting units (illustrated), and there are 
a series of coloured plates showing tints 
of typical wall-surfaces, each with the 
corresponding coefficient of reflection 

* Illum. Ekg., July, 1922, pp. 197-202. 



attached. The booklet also contains a 
scries of photographs taken by artificial 
Light, showing typical methods of lighting 
school-rooms, etc. 


The discussion on the subject of motor 
headlights before the Optical Society on 
May 11th lias now appeared in the 

Society's Transactions* and has since 
been issued in pamphlel form. The 
introductory paper read by Mr. J. W. T. 
Walsh deals mainly with the analysis of 
glare. A diagram is presented relating 
contrasl perceptible by the eye to 
brightness (candles per sq. ft.) and it is 
shown that sensibility diminishes very 
rapidly below O01 candles per sq. ft. 
Hence an inconspicuously dressed pedes- 
trian (whose clothes reflected only H» pei 
(■(■nt. of light) must receive an illumination 
of 0'3 foot-candle in order to be clearly 
revealed. The production of this illumi- 
nation at a distance of lllii feet with 
two headlights 9 in. in diameter would 
involve a brightness of the latter of at 
least 3,000 candles per sip ft. a degree 
of brightness which is almost certain to 
give rise to some glare. This shows in 
a nutshell the situation which calls for 
compromise between two conflicting 


Various devices, involving restriction 
of beam, with the object of diminishing 
glare, are described, and the recom- 
mendations of various committees in 
this country and the United States are 
quoted. Many of these aim at restrict- 
ing the beam below a horizontal plane 
a certain distance above the roadway, 
but there are various practical difficulties. 
For instance, a beam almost entirely 
confined below the horizontal may be 
unsatisfactory in regard to showing sign- 
posts, overhanging branches of trees and 
other objects above the prescribed level. 
The use of the R.A.C. standard disc is 
described and illustrated. Finally the 
question of legislative enactments is dis- 
cussed. Thirty-five American States 
demand a minimum candlepower in the 

forward direction and fifteen place an 
upper limit on candlepower above the 

* Trans. Optica! Society, 192] 2, pp. 256-294. 

horizontal. American recommendations 
provide for a laboratory test of headlights, 

but this is far from ensuring their correct 

Following Mr. Walsh's paper a great 
variety of headlights exhibited, all em- 
bodying attempts to eliminate elate, are 
illustrated. Special interest is attached 
to the C.A.V. (Grubb) headlight which 
has previously been described in this 
journal and there is a special contribution 
discussing the general problem of design 

by F. .Meyer (Carl Zeiss. Jena). 

The discussion was opened by Com- 
mander T. V. Baker, who exhibited a 
device for testing brightness and re- 
ferred to the difficulties introduced by 
cars driving at high speeds and accord- 
ingly using especially powerful lights. 
Dr. S. W. Stratton, of the Bureau of 
Standards, Washington, summarises 
American methods of testing, pointing 
out that the principle of entirely con- 
fining ligbl below the horizontal could 
not be followed rigidly and that some 
compromise was necessary : this has been 
effected by tests <>f prescribed candle- 
power at certain angles. Mr. L. Caster 
referred to various discussions before the 
Illuminating Engineering Society and to 
the joint committee which this Society 
had formed to deal with the subject ; he 
conveyed an invitation to the Optical 
Society to appoint a representative on 
this Committee. Reference was made to 
experience in other countries and to the 
distinction drawn in some German tests 
between glare that merely caused tem- 
porary discomfort, and ulare that was 
actually intolerable to the eye. The 
importance of the subject was recognised 
by the decision of the International Illu- 
mination Commission to appoint an inter- 
national technical committee to review- 
existing regulations. Mr. J. S. Dow and 
Capt. E. Stroud also joined in the dis- 
cussion, the latter presenting some photo- 
metric tests on the Holophane and other 
forms of headlights. 




[At the request of many of our readers we have extended the space devoted to 
this Section, and are open to receive for publication particulars of interesting 
installations, new developments in lamps, fixtures, and all lands of apparatus connected 
with illumination. 

The contents of these pages, in which is included information supplied by the 
makers, will, it is hoped, serve as a guide to recent commercial developments, and we 
welcome the receipt of all bona-fide information relating thereto.] 


A bulletin on Ornamental Street- 
Lighting issued by the Westinghouse 
Electric and Manufacturing Company 
(Indiana, U.S.A.) contains some pleasing 
illustrations of decorative street -lighting 
units, a feature of which is the use of 
diffusing devices to diminish glare. 
Lanterns may be divided roughly into 
two classes, those consisting of globes of 
diffusing white glass of decorative shape, 
and those using straight panes of wt Sol- 
Lux " glassware. These units are in- 
tended primarily for use with gasfilled 
lamps, and it is common practice to sub- 

divide the light by having a cluster of 
globes on the one post. 

Some data on street-lighting deserve 
notice. It is stated that in the United 
States the average cost of a complete 
installation varies from L50 to 2'00 
dollars per front foot. Whereas the 
expenditure in most other directions has 
increased considerably during recent 
years, there has been little advance in the 
cost of street-lighting, and there are few 
cities spending more than three dollars 
per capita. 

Classes of streets are classified as 
follows : — 

Type of Street. 

Size of Lamp, 

Spacing in Feet. 

Mounting Height, 
in Feet. 

Main streets 

Minor business streets 

Residential streets 

2,500— 4,000 
1,000— 2,500 




10 —11 


An interesting display of the " Kandem 
fittings for gasfilled lamps is to be seen 
in the showroom of Messrs. Justus Eck 
and S. Brook (in Palmer Street. West- 
minster). Some ot these comprise an 
over-reflector with diffusing globe below 
and are suitable for the illumination of 
factories, yards, etc., and one pattern. 
having no glass globe btit a deep reflector 

completely screening the filament, is 

stated to give 85 per cent, downward 
illumination. A pleasing type for office 
lighting, etc., comprises a bell-shaped 
reflector of white "lass with a shallow 
bowl of lighter diffusing glass below. In 
the lists referring to these fittings, polar 
curves of light distribution for each type 
are included. 

An item of interest in this showroom is 
the plug-switchboard enabling a specified 



number of linings to be 1 i ^rl it « -< 1 up in 
turn an arrangement which obviates 
the possibility of too many being con- 
nected simultaneously and the conse- 
quent blowing of a fuse 


A mow catalogue of Lanterns and 
Reflectors, issued by the Wardle Engineer- 
ing Co., Ltd. (Elsinore Road, Old 
Trafford, Manchester), deserves attention. 
We are glad to note that the firm have 
followed the practice, now becoming 
usual, of including some introductory 
notes emphasising the importance of 
good Lighting, explaining the chief terms 
used in illuminating engineering, and 
giving some indication how illumination 
may be calculated. 

in the " Workslite " section, typical 
reflectors of extensive, intensive and 
focusing patterns are illustrated. In the 
" Inverlite " section there are data, on 
some pleasing forms of semi-indirect 
units, and howl fittings, and in the 
Lantern and Street-lighting Section- we 
have various forms of units suitable 
for exterior lighting. Bach section is 
prefaced by a page of introductory 

One special development that deserves 
mention is the "girder fitting" com- 
prising a lamp in an intensive reflector 
capable of being adjusted at any angle 
for all classes of machine too! lighting. 

there will lie an "industrial showroom " 
covering a complete range of industrial 
applications of electricity, and catering 
especially for the contractor's require- 
ments. Radiophone products will also 
he on view. 

The premises will he opened on 
Thursday, December 14th. 


We notice that on October 7th the high- 
pressure public lighting installation, 
recently extended by the Dunfermline 
Corporation (Jas Department to the 
Ancient Royal Burgh of Culross, was 
toi mally inaugurated. 

The Gas Journal, in referring to this 
event, remarks that the installation is of 
special interest in view of the claim that 
Culross was the first place where gas was 
made. Here the Earl of Dundonald 
established a factory for the manufacture 
of coal tar and in the course of his 
experiments noticed the inflammable 
nature of the vapour during the process 
of distillation. Shortly afterwards the 
Earl of Dundonald came in contact with 
.Murdoch and the incident at the tar 
works was discussed. It is believed that 
this was the origin of the scheme for the 
manufacture of gas which Murdoch 
subsequently developed and turned to 
practical account. 

Now, after an interval of 140 years, 
gas is again being introduced into Culross. 


New Showroom. 

Our attention has been drawn to the 
new premises to he opened by the 
Metropolitan-Viekers Electrical Co., Ltd., 
at Daimler House, Paradise Street. 
Birmingham. Daimler House will be 
the only address in Birmingham and 
will, therefore, include, besides show- 
rooms, the whole of the Company's 
offices and stores. 

A large stock of electric lighting 
fittings of all descriptions will he main- 
tained and all kinds of domestic electric 
appliances will he on view. In addition 


We are informed that Mr. George Julius 
Webber, eldest son of Mr. Joseph Webber, 
of the Provincial Fittings Co., Ltd., at 
Pifco House, Manchester, took first -class 
honours in the LL.B. Final Examination 
of the London University, and was 
awarded the University Scholarship. 
Mr. George was called to the Bar in 
January this year, having headed the 
list in the Bar Final Examination. 
the three years' studentship of 100 
guineas per annum, and 50 guineas extra 
honorarium for good work performed. 



INDEX, October, 1922. 


Advertisement Placards, Illumination of . . . . . . . . . . 282 

Artificial Daylight, A Standard of . . . . . . . . . . . . 282 

British Commercial Gas Association. Annual Conference . . . . . . 276 

British Empire Exhibition, The 281 

Editorial. By L. Gaster . . . . . . . . . . . . . . . . 267 

Firefly as an Illuminant, The . . . . . . . . . . . . . . 285 

Illuminating Engineering Society, U.S.A., Annual Convention, Xotes on . . 279 

International Gas Exhibition in Amsterdam, The . . . . . . . . 281 

Kinema Studios, The Use of Artificial Illuminants in. By L. A. Jones 

(concluded) . . . . . . . . . . . . . . . . . . 271 

Light, The cost of now and forty years ago . . . . . . ' . . . . 284 

Lumen Measurements, Apparatus for . . . . . . . . . . . . 283 

Motor Headlights, Glare from . . . . . . . . . . . . . . 286 

"Reviews of Books and Publications Received .. .. .. .. 289 

School Lighting 285 

Topical and Industrial Section . . . . . . . . . . . . 287 


Practical Optics for the Laboratory 'nut 
Workshop. By B. K. Johnson. (Benn 
Bros., Ltd., London, 1922. 12-s. %d. 
net. pp. 189, figs. 140.) 

This little book has been written 
primarily as a course of instruction for 
the student in Practical Optics. Pro- 
fessor Cheshire, C.B.E., in a foreword, 
remarks that up to the present time 
there has been an unfortunate want of 
co-ordination between the practice of the 
laboratory and that of the workshop. 
The book aims at bridging the gap 
between practice and theory. Mr. John- 
son deals primarily with the experimental 
side of practical optics. The first chapter 
deals with sueh simple experiments as 
the verification of laws of reflection and 
refraction, and we then pass on to work 
with mirrors, lenses and prisms. Chapter 
III. deals with photometry. The Ritchie, 
Rumford and Lummer-Brodhun instru- 
ments are described and the use of the 
photometric bench illustrated. As an 
illustration of the application of photo- 
metry to optics an experiment for 
determining the loss of light in a telescope 

is described. The author has doubtless 
selected matter applying most directly 

to optics, but we think that in a sub- 
sequent edition this chapter might with 
advantage be enlarged. Some account 
of illumination photometers should surely 
be included, and their application might 
be illustrated by such experiments as 
the determination of the reflection and 
absorption coefficients of various surfaces 
and of the brightness of screens illumin- 
ated by optical lanterns and cinema 
projectors and the loss of light in such 
instruments. Generally speaking, pro- 
jection, essentially an optical problem, 
deserves more attention. Similarly, the 
next chapter on spectrometers might be 
extended to include the subject of 
spectrophotometry, which is of increasing 
practical importance. 

Other chapters deal with further 
experiments on ""thick- " lenses, refracto- 
raeters and polarised Light, and some 
useful practical hint- on cleaning optical 
glass, silvering and frosting, etc.. arc 
given in an appendix. 

Tlic paper and printing are good, and 
there are many diagrams, clearly executed, 



The Architectural Students' Handbook. 
By F. B. Yerbury. (Technical Journals 
Ltd., London, 1922. pp. 150; 22 plates.) 

Mr. Ykkimky. as the Secretary of the 
Architectural Association, is naturally 
in a favourable position to advise the 
student entering the architectural pro- 
fession, and his handbook contains much 
wise advice and practical information. 

After a preliminary chapter on entering 
the profession, the training of the archi- 
tect is discussed and particulars of 
various schools, scholarships and pro- 
fessional bodies are given. A list of 
hooks to form the nucleus of a Btudent's 
library is included and then- are brief 
sections on training in France and Italy. 
Valuable hints are added on employment 
and architectural practice and the notes 
on draughtsmanship, etching and photo- 
graphy, which are illustrated by a series 

Of plates at t lie end of t lie volume, are 

well worth study. Under the t itle ■ The 
Architectural Student's London," a list 
of public buildings which may be studied 

and sketched is included and reference is 

made to the chief museums, libraries and 


We have only one criticism to make, 

namely, that the author does not appear 
to make any reference to lighting 
subjeel which verj frequently falls under 
the direction of t he architect . t hough 
some publications on the cognate subjects 
of heat ing and ventilation are mentioned. 
We would suggest that in a forthcoming 

edition some of the standard hooks on 

this subject should be included in the 

list Of works for Si udentS to read and t hat 

some reference to t he Illuminating Engin- 
eering Society, as a body whose pro- 
ceedings are of unquestionable interest 

to architects, should be made. 

Incandescent Lighting. By S. -J. Levy'. 
(Sir Isaac Pitman db Sons, Ltd.. 
London, 1022. pp. 129. .">*. net.) 

Tins work forms one of the "Common 
Commodities and Industries Series." 
The initial chapter is devoted to a brief 
historical summary of the development 
of artificial lighting. Incandescent light- 
ing is then denned and the chief types 
of incandescent gas lamps are briefly 
described. There is also a short account 
of electric lamps and other lighting 
agents. This leads to a subsequent 
chapter dealing with the rare earth 

industry, in which the occurrence of 
monazite and the separation of thorium 

and cerium for mantles is dealt with, 

after which a chapter is devoted to 
incandescent mantle manufacture. We 
have next a comparison of cost of 
lighting by oil, gas and electricity, and a 
final chapter on " Lighting and the 
Energy Problem " containing some specu- 
la! ions on tut are developments. 


To stimulate interest in certain urgent 
electrical problems, The Electrician is 
arranging a series of competitions, and 
is allocating £250 in prize money. These 
competitions will be open to all persons 
without distinction of ape, sex or nation- 
ality, and will he held at quarterly 
intervals during 1923. The first will he 

tor design- for the cheapest and best 
electrical installation for an "all-elec- 
tric" house. Tin- second will call tor a 

solution oi the problem of how hot 
water can best he obtained electrically. 
The third will require a scheme to he 

prepared for the lii/hline; of a village hall 
electrically. It is anticipated that not 

only will some interesting solutions he 

sent ill, hut that the results will stimulate 

electrical progress and lead to t he cheaper 
and more efficient use of electricity. 

Full particulars of competitions are being 

published in The Electrician. 


We note that from October 6th onwards 
the price of Electricity (issued by S. 

Ilentell & Co., Ltd., Maiden Lane. 
W.C.2) will be restored to 2d. per issue. 
At the same time every effort will be 
made to maintain and. it possible, in- 
crease the vali E i he editorial contents. 


We understand that, commencing with 
the January issue. The Power User will 
become The Power Engineer. It is felt 
that, this title will more completely 

describe the wide scope of the journal, 
to which we wish continued success and 
prosperity under ils new name. 

THE TLLI^nXATTXC FATilNEER '(nov.-dec. 1922) 


Cosmos iLawiiDs 

Gasfilled & Vacuum 



You are perfectly safe from legal action if you stock, sell and use " COSMOS " 
LAMPS. They are fully licensed and made under British Patents Nos 23499 
of 1909, 23775 of 1912, 10918 of 1913 and others. 

" Cosmos " Lamps are made in a variety of types for a wide range of voltages 
and capacities to suit all conditions of application. 


We have at the disposal of our customers an Illuminating Engineering Section 
which has been formed to draw up complete specification for industrial, domestic 
and street lighting, and to advise in connection with all illumination problems. 
You are invited to make full use of these facilities. 

Write for particulars of trade discounts, new literature and overprinted leaflets to 

















B en/ami n 










In a large number of installations, particularly those in which the headroom 
is limited, it is practically impossible to use shallow reflectors to ensure 
wide distribution without a certain amount of objectionable glare. The 
"Anti-Glare" fitting is a practical solution of this difficulty, a wide 
distribution of light being assured, ^hile glare is eliminated by means 
of the special screen which also materially aids the light distribution. 
The inner reflector prevents any light being iost in the hood— thus all 
is utilised to the best advantage. 

Full particulars from 


Brant wood Works, Tariff Road, Tottenham, N.I 7 




Si^BEaBaaaBSI^BZ^3BB^3B^^BB !^ga5BBa^BEBgSBSS^a3Ba5Eai^BE^Baa 

Sole Agents in Australia : SMessrs. Waring, fktartin and Harris, 49, Clarence Street, Sydney. 


Holophane Lumeter 




Invaluable for the investigation 
of Lighting conditions in 
Buildings of all descriptions. 

For all particulars apply to:— 


Elverton Street, Vincent Square, 


Illuminating ISngtnrcnntj 

Founded in London, 1 909 

provides an impartial platform 
for the discussion of lighting 
problems and all illuminants. 
Forms of application for member- 
ship and all particulars may be 
obtained from the Hon. Secretary 
(Mr. L. Gaster, 32, Victoria Street, 
London, S.W.1). 




Holophane Service 

INDUSTRIAL LIGHTING must be efficient, and this 
can only be obtained by a correctly planned installation 
using scientifically constructed reflectors. 

acknowledged to be the most efficient units on the 
market; because they are scientifically constructed, and 
have behind them the 25 years' practical experience of 
the pioneers in correct illumination. 

There is a type for every class of Industrial requirement. 

Untouched night photoerapn 

Let our ILLUMINATING ENGINEERING DEPARTMENT prepare a complete lighting specification for you 


Elverton Street, Vincent Square, LONDON, S.W.1 

(3 minutes from Army & Navy Stores) 


Electric Light Fittings 

New List now Ready 


Principal Showrooms and Sales Depot : 

Magnet House. Kingsway, LONDON, W.C.2 

Brandies throughout the United Kingdom 
and in all the principal markets of the world. 






Progress in most Arts and Sciences is intermittent. 
At intervals there are noteworthy advances such 
as occurred in Electric Lighting when the Metal 
Filament (Vacuum) and Gasfilled Lamps were 

But in the intervening periods between these striking 
advances there is also progress, a process of develop- 
ment gradual but quite as important. Some of the 
developments during the past year were summarised 
at the opening meeting of The Illuminating 
Engineering Society on November 14th, 1922 (see 
p. 299 in this issue). 

It was pointed out that during the past year the 
cost of lamps had been materially reduced, that 
lamps of smaller consumption for ordinary supply 
voltages had been introduced, and that new and 
useful fittings for the application of light in practice 
had been designed. 

Issued bv the Electric Lamp JHZanufa 



\d the 


There are occasions when electric light is even 
better than daylight. 

Daylight, and especially direct sunlight, is responsible 
for rapid fading of colours, and in the case of 
priceless objects in museums this gradual deterioration 
is a matter of great consequence. 

In a recent paper before the Royal Society of Arts, 
Sir Sidney F. Harmer, Director of the Natural 
History Department of the British Museum, gave 
the results of experience on this point. With a 
view to preserving certain valuable objects it has 
even been proposed to keep the blinds down, 
leaving them in semi-darkness. 

But experiments suggest that diffused daylight is 
about six times as injurious as electric light, and 
that direct sunlight is from 20 to 70 times as 
injurious as diffused daylight. Hence it is 
suggested that rooms containing unique objects of 
more or less fugitive colours might be illuminated 
solely by electric light. 

Electric lamps can now be obtained which 
produce a satisfactory "daylight" effect. 

ssociation of Qreat ^Britain, Limited. 

viii THE ILLUMINATING ENGINEER (nov.-dkc. 1922) 



Holophane Service 



THIS is the latest type of Holophane Scientific Unit. 
It is made in two sizes, and is called the " Reflector 
Refractor." A very efficient unit, and specially 
suitable for the lighting of OFFICES, SCHOOLS, 
The services of our Illuminating Engineering Department 
in the preparation of a lighting specification are at your 
disposal. No charge is made for this service. 


Elverton Street, Vincent Square, LONDON, S.W.1 

(3 minutes from Army & Navy Stores) 


A good lighting installation need not 
be ugly. 

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Progress in Illuminating Engineering. 

In accordance with the usual custom the opening meeting of the 
Thirteenth Session of the Illuminating Engineering Society on November 
14th was devoted to reports of progress and the exhibits of Novelties in 
illumination and photometry. 

In the review of " Progress during the Vacation," contributed by the 
wiiter, the issue of the Third Report of the Home Office Departmental 
Committee on Lighting in Factories and Workshops was mentioned as an 
important event. It was explained that it proposed to arrange for papers 
before leading societies and trade associations with the object of making 
this and previous reports more familiar, both to the lighting industry and 
the general public. Other points in the report were the desirability of 
closer co-operation between architects and illuminating engineers for theii 
mutual benefit, the recognition by the Miners' Nystagmus Committee of 
the important part played by inadequate illumination in mines as one of 
the chief factors in the causation of this disease, and the valuable co-oper- 
ation of the Society with the London " Safety First " Council and the 
British Industrial ""Safety First " Association in connection with lighting 
conditions in streets and factories. Reference is also made to the compre- 

292 THE ILLUMIXATIX< ! ENGINEER (nov.-dec. 1922) 

hensive series of papers presented at the Sixteenth Annual Convention of 
the Illuminating Engineering Society in the United States and the recent 
Eleventh Annual Conference of the British Commercial Gas Association 
in this country. 

The report presented by the Committee on Progress in Electric Lamps 
and Lighting Appliances contains evidence of steady advances. Progress 
during the last year has been mainly in the form of improvements in detail 
and new applications of lamps and fittings. Attention is drawn to the 
diminution in prices of electric lamps and the introduction of gasfilled 
lamps of smaller wattage. Other items of interest have been the intro- 
duction of gasfilled lamps with opal bulbs and the " daylight " lamps 
with tinted bulbs devised for the purpose of furnishing a light suitable for 
colour-matching processes. Considerable progress is also reported in lamps 
of the projector type for use in cinematographic work and for floodlighting. 
We are glad to note the emphasis placed on co-operation between makers 
of lamps and fittings manufactures, a point on which stress has frequentlv 
been laid in this journal. Amongst new designs mention may be made of 
a new bowl having a clear glass canopy which is claimed to render the unit 
practically dust-proof, thus removing one of the greatest objections to the 
open bowl. 

As usual the exhibits of novelties at the opening meeting covered a 
wide field. Mr. W. A. Jones showed some of the dust-proof fittings referred 
to above, and Capt. E. Stroud, the new Holophane " Filterlite " semi- 
indirect fitting which appears to have several novel features. Capt. Stroud 
also exhibited the "Tuck" illumination-photometer, which is of very 
compact and ingenious design, and represents an interesting addition to 
the variety of simple apparatus of this type introduced during recent years. 
The new hospital inspection lamps shown by Rayner & Keeler, Ltd., form 
the latest development in this special device, as previously discussed at 
the joint meeting devoted to the use of light in hospitals in April last, and 
furnish an excellent example of the good results attending co-operation 
between illuminating engineers, manufacturers of optical appliances, and 
ophthalmic surgeons. The new Ceag pillarless miner's lamp, shown by 
Mr. Plummer, is an interesting development of the researches that have 
recently been initiated on lighting in mines, the importance of which was 
strikingly endorsed both at the discussion on this subject before the 
Illuminating Engineering Society in February, 1920, and again in the 
report issued this year by the " Miners' Nystagmus Committee." Other 
demonstrations included a striking demonstration by Mr. S. O. Pearson, of 
the " blinking effect " in neon lamps shunted by a condenser, some charming 
new types of illuminated signs shown by Mr. E. T. Ruthven Murray, and 
a process for impregnating silk fabrics for lamp shades developed by Mr. 
Chas. A. Selz, with the object of rendering the fabric less inflammable, easier 
to keep clean and a better diffuser of light. 

Thus, while there have been no very outstanding advances in lamps 
and lighting appliances during the past year, there has been steady progress 
in detail. There are signs that the check on development imposed by the 
war is gradually passing away and that the lighting industry is getting 
into its normal condition. We hope that when the next session of the 
Illuminating Engineering Society opens there will be other developments 
of interest to record, and that the process of recuperation will have made 
further progress. 

THE ILLUMINATING ENGINEER (nov.-dkc. 1922) 293 

The Loss of Colour in Objects exposed to Light in Museums. 

We have frequently referred to the knowledge now being gained by 
physiologists regarding the effect of light on human life. Not only do the 
sun's rays affect the pigment of the skin, but according to some researches 
by Dr. A. F. Hess and M. A. Lundagen (see p. 310) they profoundly influence 
the composition of the blood. Inanimate objects are likewise affected. 
The fading of colours when exposed to light is a matter of common know- 
ledge. ' The pitiless march of destructive forces " in museums, where 
objects of priceless value are stored, is one of the most serious problems 
with which curators have to deal. The paper on this subject recently read 
before the Royal Society by Sir Sidney F. Harmer, Director of the Natural 
History Departments at the British Museum (see pp. 308-310) is therefore 
of great interest. 

It is now recognised that fading is largely due to the rays from the 
violet and ultra-violet ends of the spectrum. Indeed, certain sources rich 
in such rays, such as the quartz tube mercury vapour lamp, have been 
specially used to test the permanency of colours. According to Dr. Russell 
and Sir Wm. Abney, fading does not occur if air and water vapour are 
excluded, but it is impracticable to enclose most exhibits in vacuo. A more 
hopeful method is to screen the objects with special glasses checking the 
passage of ultra-violet rays. But it appears that fading is not eliminated 
by this precaution, but only slowed down, being cumulative in action. 

The next point for consideration is the nature of the light by which 
specimens are illuminated. While we have hardly sufficient data to make 
very precise comparisons, Sir Sidney Harmer's experiments make it clear 
that direct sunlight is very much more injurious than diffused daylight. 
Hence the use of blinds and curtains has been suggested. But this raises 
the question how far, in order to preserve objects for the future, it is desirable 
to interfere with inspection by visitors in the present day. We have some 
sympathy with the views expressed by the Chairman (The Earl of Crawford 
and Balcarres) who said that he believed in using the good things of the 
earth and not in sacrificing too much to posterity. 

A more judicious precaution may be the use of suitable artificial light. 
There are many different forms of lamps now available, some doubtless 
less injurious than daylight, others possibly more harmful. Sir Sidney 
formed a rough estimate that electric light (presumably from incandescent 
lamps) was only one-sixth as injurious as diffused daylight. One would 
like to see more detailed scientific experiments on various artificial illumin- 
ants in comparison with daylight, due attention being given to spectro- 
scopic analysis and photometric measurements of illumination. It might 
prove desirable to illuminate certain rooms containing valuable specimens 
in fugitive colours entirely by artificial means, especially in view of the 
fact that the intensity of illumination necessary to enable the objects to be 
seen might be very much less than that furnished by daylight. If, in 
addition to securing greater immunity from fading, it was found possible 
to show colours correctly by using " artificial daylight," this might prove 
a valuable system to the curator. The problem forms part of the general 
question of the lighting of museums, and the time seems ripe for an 
exhaustive scientific inquiry. 

A 2 

2«i4 THE [LLUMINATING ENGINEER (nov. dec. L922 

A Visit to the London General Omnibus Company's Repair Works at Chiswick. 

The visit of members of the Scientific and Technical Circle of the Insti- 
tute of Journalists to the repair shops of the London General Omnibus 
Co., Ltd., at Chiswick, on November 27th, was an interesting event. The 
inspection of this unique works where the fleet of 3,000 motor-buses owned 
by the Company is kept in repair was instructive as an example of scientific 
and efficient maintenance of complex machinery, of care for the well-being 
of the human element in the factory by whom the machines are tended, 
and of consideration for the safety of the public who make use of the repaired 
vehicles. In many respects the works are a model of scientific organisation. 
Every vehicle is subjected to thorough overhauling at regular intervals. 
On arrival it is dismantled and the parts are distributed to various sections 
of the works, where they are cleaned and repaired, and finally reassembled 
on a moving platform 220 feet long, in a manner reminiscent of the methods 
of the Ford Motor Co. The engineering side of the work only began opera- 
tions in August, 192 1 ; within two months the weekly output of completely 
overhauled vehicles had reached 75 ; at the present time 120 can be dealt 
with weekly, in rush periods. Thanks to this systematic overhauling break- 
downs are rare and it is stated that in 1920 the lost mileage was only nine 
miles in 10,000. 

Many highly ingenious machines were seen in operation in these 
extensive works, notably the large automatic washing apparatus which 
serves to cleanse parts grimed and dirtied by a year's work. Equally inter- 
esting were the arrangements for painting and varnishing woodwork of 
vehicles, a process that can now be completed within five days. We 
were glad to observe that the works as a whole are lighted in an up-to-date 
manner by overhead gasfilled lamps in modern reflectors. An interesting 
device is the series of coloured lamps in various departments by which the 
attention of managers is called to attend to telephone calls, etc. The works 
are equipped with an excellent canteen, where 1,000 men can be served with 
a well-cooked dinner, and a model " First Aid " department. On a portion 
of the spare land a sports ground for the use of employees has been laid out. 

Following the inspection of the works an address on " The Safety First 
Movement in England " was delivered by Mr. H. E. Blain, C.B.E., who, 
besides being Assistant Managing Director of the London Underground 
Railways and L.G.O.Co. Group, is known to our readers as the Hon. Secretary 
of the London " Safety First " Council and the British Industrial " Safety 
First " Association. Mr. Blain gave an instructive account, illustrated 
by lantern slides showing typical posters, etc., of both branches of the 
" Safety First " movement. The subject, following as it did the inspection 
of the L.G.O. repair shops, was a most appropriate one. Readers are 
familiar with the excellent work that has been done by both these organisa- 
tions. As a result of the activities of the London " Safety First " Council 
the number of accidents in the streets of London has been materially 
diminished, notwithstanding the great increase in vehicular traffic during 
recent years. Equally striking results are recorded by members of the 
British Industrial Safety First Association, who have introduced safety 
methods in their factories. When it is realised that in 1920 as much as 
£6,000,000 was paid in workmen's compensation in connection with 3,500 
deaths and 302,000 disablements, it will be seen that there is a wide scope for 
the Association's beneficent work. The thanks of the Circle are due to 
Mr. Blain for this interesting visit, and also to the chief engineer, Mr. G. J. 
Shave, and his assistants, who accompanied the party round the work-. 

L. Gaster. 





Zhc 3lluminating Engineering Society 

(Founded in London, 1909.) 

The Illuminating Engineering Society is nut, as a body, respo)isible 
for the ojyiniuiis expressed by individual authors or speakers. 


(Proceedings at the opening meeting of the Illuminating Engineering Society, held at the 
House of the Roval Society of Arts, 18, John Street, Adelphi, W.C., at 8 p.m., on Tuesday, 
November 14th, 1922.) 

The Opening Meeting of the session 
was held at the House of the Koyal 
Society of Arts on Tuesday, November 
14th, 1922, the Chair being taken by 
Mr. J. Eck. 

The Minutes of the last meeting having 
been taken as read the Hon. Secretary 
(Mr. L. Gaster) reported that the 

The Hon. Secretary (Mr. L. Gaster) 
then presented the customary Notes On 
Events during the Vacation. Reference 
was made to the issue of the Third Report 
of the Home Office Departmental Com- 
mittee on Lighting in Factories and 
Workshops. It is hoped to arrange for 
papers before leading scientific societies 
and trade associations with the object 

following have been nominated members of making these aims more widely known. 

of Council, in accordance with the 
arrangement whereby the Presidents of 
leading kindred Associations become, 
during their tenure of office, members 
of Council of the Illuminating Engineer- 
ing Society : — 

Mr. .1. 1). Smith 

Other matters referred to included the 
Keport of the Miners' Nystagmus Com- 
mittee, the work of the British Industrial 
" Safety First " Association, and the 
desirability of co-operation between the 
architect and the illuminating engineer. 

President of the Institution of Gas 

President of the Institution of Electrical 

President of the Council of British 

President of the Ophthalmological Society. 
Chairman of the Society of British Gas 

President of the Electrical Contractors' 


The names of the following applicant's for membership were then announced : 
'Sir. W. F. Butler . . . . Secretary of Elm Works Ltd., makers of 

gas lamps and lighting appliances, 32, 

Broderick Road, London, S.W.7. 
Lt.-Col. H. M. Kirkby . . . . Consulting Engineer, 64, Riggindale Road, 

Streatham, S.VV.16. 
Mr. Charles Raphael . . . . Consulting Engineer, 35, Chase Green 

Avenue, Enfield, Middlesex. 
Mr. R. Rook Jones . . . . Electrical Engineer, 46, Queen's Road, 

Wimbledon. Surrey. 

Mr. Frank Gill. . 

Mr. L. B. Lawford 

Mr. A. Maitland Ramsay 
Mr. Albert Cliff 

Mr. H. Marryat 



Mr. .]. \Y. Elliott then presented the 
Report of the Committee on Progress in 
Electric Lamps and Lighting Appliances. 
Attention was drawn to the introduction 
of gasfilled lamps of lower consumption, 
and of lamps of this kind with opal 
bulbs. Other developments include tin- 
introduction of " Daylight " lamps, 
special lamps for projectors and new 
bowl fittings of a dustproof type 

A variety of novelties in lighting and 
illumination were then Bhown. Captain 
Iv Stroud exhibited the Tuck illumina- 
tion-photometer, which has several novel 
features, notably the inclusion of the 
dry-eel] within the tubular frame of the 
instrument, and the Holophane " Filter- 
lite," which i- a total enclosed howl 
semi-indirect lighting unit of decorative 

New types of Hospital Inspection 
Lamps were exhibited by Messrs. Rayneb 
& Keeler, Ltd. The first of these was 
a hand inspection lamp specially designed 
for use in ophthalmic work, which _ 
a well-defined circle of light and was 
equipped with a daylight filter for use 
in cases where correct appearance of 
colours was of importance. The Becond 
exhibit was a triple Operating Lamp, such 
that light from a gasfilled lamp is pro- 
jected by three distinct optical systems 
and concentrated by mirrors on the spot 
where lighl i- needed. 

Mr. \Y. Plummeb demonstrated the 

latest form of Ceag Miners' Lamp, the 
chief feature of which is the absence of 

pillars and improved distribution of 
light, which can be aided by a special 
adjustable shade. In this way an increase 
in effective illumination of 70 per cent. 

is stated to be obtained and inconvenient 
shadows are eliminated. 

Mr. S. 0. Pearson showed an ex- 
periment illustrating the " blinking 
effect " of a neon lamp shunted with a 
condenser. With suitable adjustment of 
the electric circuit frequencies between 
one Hash per second and about 8,000 per 
second were obtained, the higher fre- 
quencies being demonstrated by means 
of a loud-sounding telephone connected 
in the lam]) circuit. 

I aptain \V. J. Liberty described the 
artificial lighting of the new Port of 

London Building, which was illustrated 
by lantern slides made from photographs 
taken by Mr. J. 8. Dow. A feature was 
the general use of semi-indirect lighting 
in rooms panelled in dark wood, and 
attention was drawn to the central light- 
ing from the dome in the large main 
office, where the surroundings are light 
in colour, giving excellent diffusion. 

Mr. W. J. Jones showed some new 
types of bowl fittings having a clear glass 
canopy. While having an appearance 
similar to that of the ordinary bowl 
fitting, these anil 1 to be 

practically dustproof, thus eliminating 
one of the greatest objections to the use 

of open bowls. 

Mr. J. \V Ki.i.nni drew attention to 
the advantages of the small gasfilled 
lamps with opal bowls, with a view to 
eliminating glare, and illustrated their 
effect when used with the compact 
" Astro " intensifiers. The interior as- 
sumes a brightness almost indistinguish- 
able from that of the opal bulb, and a 
soft illumination, remarkably free from 
striatums, is the result. 

Mr. E. T. Ruthven Murray showed 
some of the latest developments in his 
special variety of illuminated signs, in 
which lettering engraved on the back 
of a sheet of plate glass is lighted up 
by lamps concealed along the edges of 
the phite. Some of these were particu- 
larly suitable for use in lifts, one showing 
the position of a lift at any moment in 
a multiple story building. 

Mr. (H.\s. SKI.Z exhibited the effect 

of a process for impregnating the surface 
of a silk shade. Fabrics so treated no 
longer allow the filament to be seen 
through the silk, and the diffusion is 
improved. Other incidental advantages 
of the process are that the silk is less 
liable to collect dust and is more easily 
cleaned, and is also much less inflammable. 

After a vote of thanks had been 
passed to the various exhibitors The 
Chairman announced that the next 
meeting would be held on Tuesday. 
December 12th, when a discussion on 
" Recent Developments and Modern Re- 
quirements in Street-lighting " would be 
opened by Mr. Haydn T. Harrison. 




By L. Gaster (Hon. Secretary). 

(Presented at the Opening Meeting of the Illuminating Engineering Society, held at the House 
of the Royal Society of Arts, 18, John Street, Adelphi, London, W.C., at 8 p.m., on 
Tuesday, November 14th, 1922.) 

It is customary, at the first meeting 
of the session, to give some account 
of progress during the vacation. It is 
gratifying to record that Sir John 
Herbert Parsons has kindly consented 
to continue in office as President during 
the present session. It will also be 
recalled that at the Annual Meeting, 
May 25th, three additions were made 
to the Council, namely, Dr. J. F. 
Crowley, Mr. Philip Sugg and Mr. 
D. R. Wilson. 

In the Report of the Council for the 
past session reference was made to the 
urgent need for great support and 
increased membership in order that 
the Society may extend its activities 
and realise, on a greater scale, the 
objects for which it was created. A 
sub-committee of the Society has, 
accordingly, been formed to consider 
means of propaganda and methods of 
increasing the membership and influence 
of the Society. A special issue of The 
Illuminating Engineer has also been 
prepared, containing a list of all papers 
and discussions before the Society since 
its commencement, and a review of 
the progress of the Illuminating Engineer- 
ing movement since its inception. It is 
hoped that this special issue will prove 
valuable in showing the scope and 
variety of the work already done, and the 
need for further support in order that 
the activities of the Society may be 
in future conducted on a scale com- 
mensurate with the importance of its 
aims and objects. 

An event of outstanding importance 
has been the issue of the Third Report 
of the Home Office Departmental Com- 
mittee on Lighting in Factories and 
Workshops, the contents of which have 
been dealt with in the special issue 
of the Illuminating Engineer referred 
to above. After summarising recom- 
mendations contained in previous reports 

on the subject of glare, avoidance of 
shadows, etc., it is pointed out that 
further research is necessary before 
legal standards for working illumination 
can be framed. This matter, it is 
suggested, should be studied in co- 
operation with the chief industries con- 
cerned, but meanwhile minimum values 
illustrative of good practice are recom- 
mended for fine work (requiring three 
foot-candles) and very fine work (requir- 
ing five foot-candles). The original 
scheme of work of the Committee has 
been curtailed by the urgent demands 
in the interests of national economy, 
and it is, therefore, of importance 
that the aims of the Committee should 
be made familiar, both to the lighting 
industry and to managers of factories, 
and their aims fully understood. It is 
hoped to arrange for several papers 
before leading scientific societies and 
trade associations with the object of 
making these aims widely known. 

Great interest also attaches to the 
Report of the Miners' Nystagmus Com- 
mittee issued by the Medical Research 
Council, and also summarised in the 
special issue of the Illuminating 
Engineer mentioned above. The chief 
conclusion of the Committee, that the 
essential factor in the production of 
miners' nystagmus is deficient illumina- 
tion, is in accordance with the general 
view expressed in the discussion on 
this subject before the Illuminating 
Engineering Society in February, 1920. 
Various improvements, such as an 
increase in the illuminating power of 
miners' lamps to 2—3 candles, are 
suggested, and the report will, no doubt, 
have a beneficial influence in raising 
the standard of illumination in mines. 
The subject of street-lighting has been 
receiving attention, several new schemes 
having been recently introduced in 
Oxford Street and elsewhere in London, 



while in some provincial cities sub- 
stantial economies coupled with improve- 
ments in illumination, have been effected 
by the substitution of the latest super- 
heated inverted gas burners for those of 
.in obsolete type. Street-lighting as a 
factor in " street safety" lias also been 
receiving attention from the London 
"Safety First" Council, with whom 
the Society continues to co-operate, 
and statistics have been published in 
the United States Leading to the eon- 
elusion that 17'6 per cent, of street- 
accidents occurring at night are due to 
inadequate lighting. In view of the 
importance of the subject arrangements 
have been made for a discussion on 
street-lighting to take place at a meeting 
of the Illuminating Engineering Society 
on December 12th, in which the Institu- 
tions of Gas and Electrical Engim 
the Institution of Municipal and County 
Engineers, and other bodies interested 
have been invited to co-operate. 

The British Industrial " Safety First "' 
Association has recently devoted special 
attention to the analysis of accidents 
in factories, reference to which is made 
in the Journal of this Association 
(Safety First) now being issued in a 
new and expanded form. A contri- 
bution by the writer to this Journal 
emphasised the importance of classifica- 
tion of accidents with a view to determin- 
ing more fully their relation to Inadequate 
lighting, and this matter will, no doubt. 
receive attention from the Association 
in due course. 

Yet another recent event of interest 
was the Eleventh Annual Conference of 
the British Commercial Gas Association 
in Bristol during October 16th-18th, 
when a number of papers illustrating 
the applications of gas in the public 
service were presented. Of these special 
interest attaches to that by Mr. Robert 
Watson on " Modern Gas Lighting, with 
special reference to the Illumination of 
Factories and Workshops." After tracing 
recent developments in gas lighting, Mr. 
Watson referred in detail to. the recom- 
mendations of the Home Office Committee 
on Lighting in Factories and Workshops 
and to recent codes of industrial lighting 
adopted in the United States, and con- 
cluded by emphasising various funda- 
mental principles in modern methods of 

illumination and showing the wide Held 
that exists for the application of scientific 
methods in gas lighting. 

The discussion before the Society 
on the Lighting of Public Buildings in 
March last has attracted, much attention, 
and the Royal Institute of British 
Architects have reprinted a summary 
of this discussion in their official journal. 
Tins step will doubtless prove useful 
in leading architects to study illumination, 
and it is of interest to mention that a 
paper dealing with various aspects of 
illuminating engineering is to be read 
before this body on November 20th. 

A variety of papers was read at the 
Sixteenth Annual Convention of the 
Illuminating Engineering Society in the 
United States during September 25th 
28th, and the proceedings on this 
occasion appear to have been of a 
particularly interesting character. 

Reports of Committees on Progress, 
Nomenclature and Standards, Education 
in Illuminating Engineering, and Motor 
Vehicle Lighting were presented. A 

special feature was a series of con- 
tributions entitled " A Fifteen Year 
Advance in the Art of Lighting." Other 
papers dealt with "Lighting for the 
Food Industry," " The Lighting of 
Motion Picture Studios." and " Screen 

Brightness," and " Office Lighting from 
the Viewpoint of Hygiene." There were 
also contributions on various aspects 
of photometry such as Flicker-Photo- 
metry, the Plotting of Spectro-photo- 
metric curves, etc. 

The latest issue of this Society's 
transactions contains an account of the 
lighting of the Milwaukee Art Institute 
which has sonic novel features. Besides 
utilising artificial daylight the arrange- 
ment provides for overhead lighting 
through areas on the ceiling adjacent 
to the walls, no light being directed 
through the centre of the skylight. 
The object of this is to avoid trouble- 
some reflections from the glass of 
pictures, a problem dealt with in con- 
nection with the natural lighting of 
picture galleries in the paper on the 
Lighting of Public Buildings read before 
the Illuminating Engineering Society 
in London in March last. 

Attention may also be drawn to an 
important " Light and Air " judgment 



in Bradford where an injunction was 
sought to restrain the Bradford Corpora- 
tion from erecting an electric light 
station, which, it was claimed, would 
cause an obstruction to the light of 
the windows of neighbouring premises. 
The. judgment of Mr. Justice Eve in 
favour of the defendants was important 
in view of the value attached by him 
to precise photometric tests undertaken 
by a member of this Society, Mr. P. J. 
Waldram. The case marks a useful 
precedent as indicating the growing 
recognition of the utility of scientific 
treatment of the subject, including the 

presentation of data based on actual 
measurements of light and illumination. 
In conclusion, it may be added that the 
National Illumination Commission is con- 
tinuing its work, and that the Chairman's 
address for the past year, and a summary 
of the present position in regard to 
Photometric Units and Definitions, is 
being published in The Illuminating 
Engineer. The writer has just heard 
from one of our corresponding members, 
Prof. M. de Chatelain, that a special 
Commission on Illuminating Engineering 
has been formed by the Central Electro- 
technical Council in Russia. 


Report of the Committee on Progress in Electric Lamps and Lighting Appliances (Mr. S. H. Callow 
(Chairman), Mr. J. E. Edgecombe, Mr. J. W. Elliott (Sec